Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OCR A Level Chemistry > Paper 3A Part 1 > Flashcards

Paper 3A Part 1 Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Definition of Relative Atomic Mass (Ar)

A

Weighted mean mass of an atom relative to 1/12th the mass of an atom of carbon 12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Definition of Relative Formula Mass (Mr)

A

The term used when working out the calculation for compounds with giant structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Name 3 types of giant structures

A

Giant IonicGiant CovalentGiant Metallic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Definition of Relative Molecular Mass

A

The term used when working out the calculation for compounds that are simple molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Name a type of simple molecular structure

A

Covalent Compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the formula for finding out how much of a compound is made up of a particular element?

A

% of element = ((number of atoms of element x relative atomic mass of the element) / relative formula mass of compound) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the molar mass?

A

.The mass per mol of a substance in g mol^-1.Same number as Mr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the amount of substance + unit?

A

.A means of counting the number of particles in a substance.Unit is the mol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is Avogadro’s Constant?

A

(NA) 6.02x10^23 mol-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is everything measured relative to?

A

Carbon-12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define the mole

A

The amount of any substance containing as many elementary particles as there are carbon atoms in 12 grams of carbon-12 (6.02x10^23) particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

number of mols (mol) =

A

mass (g) / molar mass (g mol-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Smallest mass of an atom

A

1.67x10^-27

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The largest mass of an atom

A

4.52x10^-25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do we use the smallest mass of an atom to do?

A

Produce a relative scale called the unified atomic mass unit ‘u’ = 1.67x10^-27

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

If hydrogen-1 = 1u, what does carbon-12 =?

A

12u

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Define relative isotopic mass

A

The mass of an atom of an isotope relative to 1/12th the mass of a carbon 12 atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is 1/12th the mass of a carbon-12 atom?

A

1u

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define relative atomic mass

A

The relative atomic mass is the ‘weighted mean’ mass of an atom relative to 1/12th the mass of a carbon-12 atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

formula to find out relative atomic mass/weighted mean?

A

((mass x abundance) + (mass x abundance)) / 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define molecular formula

A

The number and type of atoms of each element in a molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Define empirical formula

A

Shows the simplest whole number ration of atoms of each element in a compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

State the steps for finding the empirical formula

A
  1. find the mass2. calculate the moles3. divide all the results by the smallest value to get the ration4. adjust the ratio to get whole numbers5. workout the empirical formula
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is water of crystallisation?

A

Water molecules that are bonded into a crystalline structure of a compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What doe solid compounds formed from aqueous solutions have trapped in their crystal structures?

A

The crystals that are formed have water molecules trapped in the crystal structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What does copper sulphate exist as?

A

Blue crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does copper sulphate lose its water?

A

Heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What colour is anhydrous copper sulphate?

A

White

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the formula of copper sulphate?

A

CuSO4.xH2Ox = number of water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Anhydrous definition

A

Contains no waters of crystillisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Hydrated definition

A

A crystallised compound containing water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Where is the water in copper sulphate?

A

Water forms part of the crystal sturcture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Four steps of the hydrated and anhydrous practical

A
  1. Weigh an empty crucible2. Add the hydrated salt into the weighed crucible, weigh the crucible and the hydrated salt3. Using a pipe clay triangle, support the crucible containing the hydrated salt on a tripod. Heat the crucible and contents gently for about one minute. Then heat it strongly for a further three minutes.4. Leave the crucible to cool. Then weigh the crucible and anhydrous salt
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is a binary compound?

A

Binary compounds contain 2 elements only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How to name a binary compound with one example

A

To name it, take the first element then change second elements name to –ide (for ionic compounds the metal always comes first) for example magnesium oxide (MgO), sodium chloride (NaCl), Calcium sulphide (CaS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is a polyatomic ion?

A

Ions comprised of more than one atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What are brackets in formulas used for?

A

Polyatomic ions need to go into brackets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is a redox reaction?

A

When reduction and oxidisation happen at the same time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is OILRIG

A

OxidisationIsLossReductionIsGain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What assumptions were made during the copper sulphate anhydrous and hydrated salt experiment? Any extra infomation (how to prevent/any problems that could arise)

A

.That all the water has been lost – could heat the mass then weigh and repeat till it stays the same to counteract this.No further decompositions – copper oxide might have been made if we heated it too much

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

When are you allowed to use half values for equation balancing?

A

In combustion equations, specifically on the oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

In what order do you balance combustion equations (hydrocarbons)?

A

Carbon first then the hydrogen before finally the oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What does aqueous mean?

A

Dissolved in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Equipment needed for the determination of the formula for magnesium oxide practical

A

.access to balance accurate to two decimal places.Crucible and lid.bunsen burner.Tripod stand.heat-proof mat.clay pipe triangle.Tongs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Health and Safety for the determination of the formula for magnesium oxide practical

A

.Wear eye protection at all time (safety goggles).Take care not to touch any apparatus that is hot.Take particular care at steps 3 and 4, do not look at any bright light given off by the reacting magnesium while it is being heated.Do not place the magnesium ribbon directly in the Bunsen flame

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Method for the determination of the formula for magnesium oxide practical

A
  1. Measure the mass of crucible and lid2. Put the magnesium ribbon to the crucible. You will need to coil the magnesium so that it fits. Reweigh the crucible and lid.3. Arrange the equipment with a tripod on a heatproof mat, a clay pipe triangle on the tripod, a crucible in the triangle and a bunsen burner under it. Raise the crucible lid slightly using tongs to control the reaction4. When the reaction is nearly complete, place the crucible lid on the heatproof mat and heat the crucible strongly for 5 minutes. During this time, tap the magnesium oxide gently with tongs to break up the residue5. Allow the crucible to cool and reweigh the crucible, its contents, and lid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is molar gas volume?

A

The molar gas volume is the volume per mole of gas molecules at the stated temperature and pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What are the conditions at RTP?

A

Conditions: RTP, Room temperature and pressure20’C101KPa (1atm) pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

At RTP what does 1 mole of gas have a volume of?

A

24dm^3 (24000cm^3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is the volume and molar gas volume equation?

A

amount n (mol) = Volume V / molar gas volume V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

How is a gas a ‘perfect’ or ‘ideal’ gas?

A

If it obeys the ideal gas equation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

When is a gas most close to obeying the ideal gas equation and why?

A

real gases obey the equation very closely at low pressure (no more than atmospheric pressure) and high temperature (room temperature). Under these conditions a gas is most like a gas and least like a liquid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What 5 assumptions does the kinetic theory make about gas molecules?

A

• The particles are moving in straight lines at random.• We can neglect the volume of the particles themselves in comparison with the total volume of the gas (occupy negligible volume).• The particles do not attract one another (exert no force on one another).• The kinetic energy of the particles is proportional to the temperature of the gas.• No energy is lost in collisions between particles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is the ideal gas equation?

A

pV = nRT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

In the ideal gas equation what is ‘p’ and what is it measured in?

A

Pressure, measured in Pa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

In the ideal gas equation what is ‘n’ and what is it measured in?

A

Amount of gas, measured in mol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

In the ideal gas equation what is ‘T’ and what is it measured in?

A

Temperature, measured in K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

In the ideal gas equation what is ‘V’ and what is it measured in?

A

Volume, measured in m^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

In the ideal gas equation what is ‘R’ and what is it measured in?

A

Ideal gas constant, measured in J/mol/K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What is the ideal gas constant?

A

8.31 J/mol/K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

How to convert from cm^3 to m^3

A

x10^-6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

How to convert from dm^3 to m^3

A

x10^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

How to convert from ‘C to K?

A

273

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

How to convert from KPa to Pa?

A

x10^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Max number of electrons in the first shell?

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Max number of electrons in the second shell?

A

8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Max number of electrons in the third shell?

A

18

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Max number of electrons in the fourth shell?

A

32

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What is an electron shell?

A

A group of atomic orbitals with the same principal quantum number, n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What’s the principal quantum number?

A

Represented as n, a number representing the overall energy level of the orbital. The bigger the number, the further the distance between the energy level and the atomic nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Formula to work out how many electrons in the shell?

A

2(n^2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What is an orbital?

A

A region of high probability within an atom that can hold 2 electrons with opposite spin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What are shells made up of?

A

Orbitals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What did Pauli discover in 1924?

A

.Orbitals only hold 2 electrons.Electrons carry a negative charge.Spin on-axis - generate a magnetic field.Spin clockwise or anti-clockwise, represented by arrows.Electrons in the same orbital must spin in different directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What does an s-orbital look like?

A

A sphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Which shells have s-orbitals?

A

From n=1 onwards, each shell contains one s-orbital (max two electrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What does a p-orbital look like?

A

Dumbbell shaped, like a balloon squashed in the middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

Which shells have p-orbitals?

A

From n=2 onwards, each shell contains three p-orbitals (max 6 electrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Which shells have d-orbitals?

A

From n=3 upwards, each shell has 5 d-orbitals (max 10 electrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Which shells have f-orbitals?

A

From n=4 onwards, each shell has 7 f-orbitals (max 14 electrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

What does each part of the notation 1s^2 represent?

A

1 = energy levels = type of orbital2 = number of electrons in orbital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

What is Aufbau’s principle?

A

Electrons fill the lowest energy orbitals in sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

What is the order that the orbitals fill up?

A

1s 2s 2p 3s 3p 4s 3d 4p 5s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

What is an electron energy level made up of?

A

An electron energy level is made up of atomic orbitals with the same principal quantum number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

What is a sub-shell?

A

Within each shell, orbitals of the same type are grouped together as a sub-shellsEach sub-shell is made up of only one type of orbital only, so there are s, p and d sub-shells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

What is Hunds Rule

A

Electrons singly occupy orbitals before pairing up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

When ionising, using the orbital model, which electrons are lost?

A

The ones in the outer shell, so even if 3d has electrons in it they will be lost from 4s when ionising

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

Which two elements don’t follow Aufbau’s principle?

A

Copper and Chromium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

How does Copper not follow Aufbau’s principle?

A

copper steals a 4s electron to gain a full 3d orbitalIt’s actually 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

How does chromium not follow Aufbau’s principle?

A

chromium steals a 4s electron to be able to put an electron in every 3d orbitalIt’s actually 1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

How do copper and chromium gain stable structures?

A

Cr and Cu get stable structures from full and half full 3d sub shells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

What do the big numbers in equations show?

A

The molar ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

What are atoms trying to achieve when they bond?

A

A full outer shell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

4 key things about ionic bonding

A

Between metals and non-metalsIts to do with the loss and gain of electronsMetals form positive chargesNon-metals form negative charges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

How does an atom gain a positive charge?

A

It loses electrons, therefore there are more protons than electorns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

How does an atom gain a nagative charge?

A

It gains electrons, therefore there are less protons than electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

What is an ion?

A

A charged particle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

How do ionic bonds stay together?

A

The electrostatic attraction between the positive and negative ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

What do you use the crosses and dots for on ionic bonding diagrams?

A

use crosses for the metals electrons and dots for the non-metals electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

What is a lattice?

A

A lattice is a regular repeated three-dimensional arrangement of atoms, ions, or molecules in a metal or other crystalline solution.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

What is the structure of ionic compounds like?

A

A giant ionic lattice, the attraction between the oppositely charged ions acts equally in all directions, which leads to the formation of a giant ionic lattice in three dimensions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

Moles equation with concentration and volume

A

Mol = (cm^3 x moldm^-3) / 1000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

Rearrange the moles equation with concentration and volume for concentration =

A

moldm^-3 = (mol x 1000) / cm^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

What are almost all ionic compounds at room temperature?

A

solids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

Why are almost all ionic compounds solid at room temperature?

A

At room temperature there is insufficient energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions in the giant ionic lattice, high temperatures are needed to provide this energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

Why is the melting points higher for ionic lattices containing ions with greater ionic charges? What else does ionic attraction depend on?

A

The melting points are higher for lattices containing ions with greater ionic charges, as there is a stronger attraction between ions.The ionic attraction also depends on the size of the atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

Melting point of NaF

A

993’C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
108
Q

Melting point of CaF2

A

1423’C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
109
Q

Melting point of Na2O

A

1275’C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
110
Q

Melting point of CaO

A

2614

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
111
Q

What do many ionic compounds dissolve in?

A

Polar solvents like water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
112
Q

Why might an ionic compound not be soluble?

A

.Polar water molecules break down the lattice and surround each ion in the solution.But in a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattice structure, and the compound will then not be soluble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
113
Q

Solubility of NaCL at 20’C

A

6.1 mol dm^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
114
Q

Solubility of CaCl2 at 20’C

A

0.67 mol dm^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
115
Q

Solubility of Na2CO3 at 20’C

A

2.0 mol dm^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
116
Q

Solubility of CaCO3 at 20’C

A

1.3x10^-4 mol dm^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
117
Q

What 2 processes does solubility require?

A

.The ionic lattice must be broken down.The water molecules must attract and surround the ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
118
Q

What does the solubility of an ionic compound in water depend on?

A

on the relative strengths of the attractions within the giant ionic lattice and the attractions between ions and water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
119
Q

As the solubility decreases in ionic compounds…

A

ionic charge increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
120
Q

When does and when doesn’t an ionic compound conduct electricity?

A

.In the solid state, an ionic compound does not conduct electricity.But once melted and dissolved in water the ionic compound does conduct electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
121
Q

Describe an ionic compounds electric properties in solid state

A

.The ions are in a fixed position in the giant ionic lattice.There are no mobile charge carriers, as the ions cannot move.An ionic compound is a non-conductor of electricity in the solid state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
122
Q

Describe an ionic compounds electric properties in a liquid or dissolved state

A

.The solid ionic lattice breaks down.The ions are now free to move as mobile charge carriers.An ionic compound is a conductor of electricity in liquid and aqueous states

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
123
Q

Summarise the properties of ionic compounds

A

Most ionic compounds – .Have high melting and boiling points.Tend to dissolve in polar solvents such as water.Conduct electricity only in the liquid state or aqueous solutions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
124
Q

What is the main component in teeth, bones and tooth enamel

A

hydroxyapatite, Ca5(PO4)3OH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
125
Q

What allows tooth decay?

A

Acid conditions, from food, break down enamel and allow tooth decay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
126
Q

What does saliva do?

A

Salvia helps to neutralise acidic food and also to replace ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
127
Q

How do fluoride ions help teeth?

A

.Fluoride ions help to replace lost ions by forming fluoropatite, Ca5(PO4)3F, which is stronger than hydroxyapatite and more resistant to acid conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
128
Q

What do most toothpastes and some water sources contain?

A

Most toothpastes contain fluoride as sodium fluoride, your water may also contain fluoride depending on where you live

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
129
Q

What is the theoretical yield?

A

The maximum possible amount that can be made

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
130
Q

Why is the theoretical yield never achievable?

A

.The reactions may have not gone to completion.Other reactions (side reactions) may have occurred.Purification of the product may have resulted in loss of product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
131
Q

Percentage yield % =

A

(actual yield mol / theoretical yield mol) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
132
Q

Describe the use of aqueous barium chloride in qualitative analysis

A

Test for sulphate ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
133
Q

What is atom economy?

A

A measure of the proportion of reactants included in the final useful product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
134
Q

What happens in an ideal reaction, in terms of atom economy?

A

All reactant atoms end up within the useful product molecule, no waste produced!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
135
Q

What do inefficient reactions have in terms of atom economy?

A

They are wasteful and have a low atom economy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
136
Q

What do efficient reactions have in terms of atom economy?

A

.High atom economy.Important for sustainable development.Conserve natural resources and create less waste

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
137
Q

What is a bonding pair?

A

A pair of electrons in a covalent dot n cross diagram that are being used in the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
138
Q

What is a lone pair?

A

A pair of electrons in a covalent dot n cross diagram that are not being used in the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
139
Q

How is a sigma bond formed?

A

The head-on overlap of orbitals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
140
Q

In hydrogen what happens in covalent bonding, in terms of orbitals

A

The two 1s orbitals overlap and they become a molecular orbital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
141
Q

How is the octet rule broken in Boron trifluoride?

A

It becomes an electron deficient molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
142
Q

How can the octet rule be broken in sulphur hexafluoride?

A

3rd shell of S can hold 18 electrons, octet rule can be broken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
143
Q

What is NH4 ^+

A

Ammonium ion, a type of molecular ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
144
Q

What is a dative covalent bond?

A

A bond formed when both electrons in the share are donated by one atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
145
Q

For an exam question what should you do?

A

READ IT ALL AND DO EVERYTHING IT TELLS YOU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
146
Q

Properties of simple covalent molecules

A

.Low melting and boiling points.Weak intermolecular forces.Not soluble in polar solvents – only in other non-polar liquids.Molecules are not charged so they don’t conduct electricity (no mobile charges).Weak and soft when solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
147
Q

What does VSEPR theory stand for?

A

.Valence.Shell.Electron.Pair.Repulsion.Theory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
148
Q

What is the shape of a molecule or ion determined by?

A

The shape of a molecule or ion is determined by the number of electron pairs in the outer shell of the central atom, more specifically the number of electron pairs repelling as far away from each other as possible (maximum repulsion).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
149
Q

What is the valence shell?

A

The outer shell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
150
Q

the bond angle of a linear molecule

A

180’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
151
Q

the bond angle of a triangular planar shape

A

120’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
152
Q

the bond angle of a tetrahedron

A

109.5’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
153
Q

the bond angle of an octahedron

A

90’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
154
Q

Molecular formula of hydrochloric acid

A

HCl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
155
Q

Molecular formula of sulphuric acid

A

H2SO4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
156
Q

Molecular formula of nitric acid

A

HNO3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
157
Q

Molecular formula of ethanoic acid

A

CH3COOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
158
Q

Molecular formula of sodium carbonate

A

Na2CO3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
159
Q

Molecular formula of sodium hydroxide

A

NaOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
160
Q

Molecular formula of pottasium hydroxide

A

KOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
161
Q

Molecular formula of phosphoric acid

A

H3PO4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
162
Q

Define hydrogen ion

A

An ion with no electrons and 1 proton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
163
Q

Define acid

A

In water an acid releases hydrogen ions into the solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
164
Q

Define strong acid

A

Releases all of its hydrogen ions into the solution and completely disassociates, this is irreversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
165
Q

Define weak acid

A

Only releases a small number of its hydrogen ions into the solution and partially disassociates, this is reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
166
Q

How is sulphuric acid both a strong and weak acid?

A

Sulphuric acid is both strong and weak, it can form 2H+ and SO42- or H+ and HSO4-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
167
Q

Define a base

A

A compound that neutralises an acid, by accepting a hydrogen ion to form a salt – for example ammonias, hydroxides, carbonates and metal oxides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
168
Q

Define an alkali

A

A type of base that dissolves in water to form hydroxide ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
169
Q

Define a salt

A

The product of a reaction in which the H+ ions from the acid are replaced by the metal or ammonium ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
170
Q

Describe and explain the conductivity of sodium Na, chlorine Cl2, and sodium chloride NaCl (6 marks)

A

.Sodium is a metal and conducts as both a solid and liquid.Free moving delocalised electrons to carry the charge.Chlorine is a small simple molecule that does not conduct.No free moving delocalised electrons to carry the charge.Ionic bond between sodium and chlorine to form sodium chloride, conducts as molten or aqueous but not when solid.Free moving ions when molten and aqueous so can conduct as they carry the charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
171
Q

Why is the shape of PCl5 special?

A

Trigonal bi-pyramidBond angles of 120’ and 90’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
172
Q

Describe and explain the shape of a NH3 molecule

A

3 bonding pairs + 1 lone pair = 4 electron pairsSo repels to corners of tetrahedronDon’t see the lone pair so therefore the shape is pyramidal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
173
Q

Bond angle of NH3

A

107’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
174
Q

Why do lone pairs of electrons have greater repulsion

A

not attracted by nuclei unlike bonding pairs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
175
Q

What is the order of repulsion?

A

LP:LP > LP:BP > BP:BP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
176
Q

By how much does one LP in a tetrahedron reduce the bond angle by?

A

2.5’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
177
Q

Bond angle of H2O and why?

A

109.5 – 2.5 – 2.5 = 104.5’2 x LP’s so (– 2.5’) 2 times to the bond angle on a tetrahedron (109.5)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
178
Q

Why is CO2 linear?

A

C has 2 electron regions (2 BP’s) so it is linear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
179
Q

Define electronegativity

A

a measure of the tendency of an atom to attract a bonding pair of electrons within a covalent bond.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
180
Q

Where are the electrons positioned when both atoms in a bond are identical?

A

When the 2 atoms are identical, the electrons are shared equally and stay in the middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
181
Q

What did Linus Pauling invent and when?

A

Linus Pauling – invented the Pauling scale in 1932 which measures electronegativity on an atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
182
Q

Why does it get more reactive as you go down group 1?

A

More reactive as you go down the groupLess nuclear attraction to the outer electronEasier to loseThe nucleus is being shielded by the electrons in-betweenSo the electron feels less nuclear attraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
183
Q

Across a period what happens to the electronegativity?

A

increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
184
Q

Down a group what happens to the electronegativity?

A

decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
185
Q

Why does electonegativity increase across a period?

A

.Size roughly equal across period with same shielding by 2, 8.Nuclear charge increases across period therefore greater nuclear attraction so electronegativity increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
186
Q

Why does electonegativity decrease down a group?

A

.Down group size of atom increases.Shielding of outer shell increases.This reduces the nuclear attraction and electronegativity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
187
Q

In a bond, what happens if one atom is more electronegative than the other? Example.

A

.The more electronegative atom will have a greater share of the electrons.Take H and Cl as an example.H = 2,1, Cl = 3.0.Cl more electronegative so the electrons are attracted more towards it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
188
Q

What does delta +/- mean?

A

means it has a slight positive or negative charge now

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
189
Q

When H reacts with Cl what happens to its electron density?

A

.H has lost a small amount of electron density – becomes s+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
190
Q

What type of molecule is H-Cl?

A

Polar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
191
Q

Why is H2O a polar molecule?

A

the dipoles act in the same direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
192
Q

Why is Carbon Dioxide a non-polar molecule?

A

Symmetrical dipoles will cancel each other out, so CO2 is non-polar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
193
Q

What atom gets the delta- charge?

A

The more electronegative atom will take the s- charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
194
Q

Can you predict bonds from eletronegativity?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
195
Q

If there is no difference between electronegativity there is what sort of bond?

A

non-polar covalent bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
196
Q

If there is a small difference (0 to 1.8) between electronegativity there is what sort of bond?

A

polar covalent bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
197
Q

If there is a large difference (>1.8) between electronegativity there is what sort of bond?

A

ionic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
198
Q

metal + hydrochloric acid –>

A

metal chloride + hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
199
Q

Metal + sulphuric acid –>

A

metal sulphate + hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
200
Q

Metal + nitric acid –>

A

Metal nitrate + hydrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
201
Q

Metal + phosphoric acid –>

A

Metal phosphate + hydrogen

202
Q

Metal oxide + acid –>

A

Salt + water

203
Q

Metal hydroxide + acid –>

A

salt + water

204
Q

Metal carbonate + acid –>

A

salt + carbon dioxide + water

205
Q

Ammonia + acid –>

A

ammonium salt

206
Q

Where to observe the meniscu

A

eye level

207
Q

What is weighing by difference?

A

With weighting boat – used weighing boat = mass

208
Q

What is an intramolecular force?

A

strong bonds inside molecules

209
Q

What is an intermolecular force?

A

act between different molecules, weak compared to covalent bonds

210
Q

What are intermolecular forces caused by?

A

Intermolecular forces are caused by weak attractive forces between very small dipoles in different molecules

211
Q

3 types of intermolecular forces and their relative strength if ionic and covalent are 1000

A

Hydrogen Bonds 50Dipole-dipole forces 10London forces 1

212
Q

What is a dipole dipole force?

A

permanentA weak attractive force between permanent dipoles in neighbouring polar molecules

213
Q

Explain HCl as an example of dipole dipole intermolecular force

A

Take HCL, H is s+ and Cl s-, these charges weakly attract opposite charges in neighbouring molecules

214
Q

In London forces as the number of electrons increase …

A

so does the strength of the London Forces due to larger instantaneous dipoles created.

215
Q

In terms of intermolecular forces what can and cant dissolve in water

A

If no permanent dipoles it can’t dissolve in water, London forces don’t count as they are temporary dipoles

216
Q

How do London forces work?

A

.Movement of electrons produces a changing dipole in a molecule.At any instant, an instantaneous dipole will exist, but its position is constantly shifting.The instantaneous dipole induces a dipole on a neighbouring molecule.This induced dipole induces further dipoles on neighbouring molecules, which then attract one another

217
Q

How to find uncertainty?

A

Half the smallest possible unit you can make

218
Q

Percentage uncertainty =

A

(uncertainty of equipment/size of measurement) x 100

219
Q

What anomalous properties does water have?

A

Elevated melting and boiling points Ice floats (solid is less dense than the liquid)relatively high surface tension and viscosity

220
Q

Why does water have an elevated melting and boiling point?

A

due to strong H bonds between molecules

221
Q

Why does ice float?

A

as liquid water freezes the molecules arrange themselves in a more open, regular lattice structure

222
Q

What is a hydrogen bond?

A

A strong dipole-dipole attraction between .An electron-deficient hydrogen atom on one molecule (O-HS+ or N-HS+)and .A lone-pair of electrons on a highly electronegative atom on a different molecule (H-OS- or H-NS-)

223
Q

Why does water have relatively high surface tension and viscosity?

A

The hydrogen bonds

224
Q

In what compounds are hydrogen bonds useful?

A

organic compounds containing O-H and N-H bonds (alcohols, carboxylic acid etc)

225
Q

What are hydrogen bonds responsible for the shape of?

A

They are responsible for shape of proteins and even DNA

226
Q

New concentration equation

A

New conc = (original volume / new volume) * original conc

227
Q

Define oxidation number

A

A measure of the number of electrons that an atom uses t bond with an atom of another element. Oxidation numbers are derived from a set of rules.Also known as an element’s oxidation state

228
Q

What is the oxidation number of a neutral element?

A

zero

229
Q

What is the oxidation number of a monatomic ion?

A

The same as the charge of the ion

230
Q

What is the sum of all oxidation numbers in a neutral compound?

A

zero

231
Q

What is the sum of all oxidation numbers in a polyatomic ion equal to?

A

the charge on the ion

232
Q

What is the oxidation number of groups 1-3 in compounds

A

In compounds the elements of:Group 1 have an oxidation number of +1Group 2 have an oxidation number of +2Group 3 have an oxidation number of +3

233
Q

What is the oxidation state of hydrogen in a compound? What if it is in a binary metal hydride? What is a binary metal hydride?

A

The oxidation state of hydrogen in a compound is usually +1. If the hydrogen ion is part of a binary metal hydride (compound of metal and some hydrogen), then the oxidation state is -1.

234
Q

What is fluorines oxidation number in compounds?

A

Fluorine has an oxidation number of -1 in compounds.

235
Q

What is the oxidation state of oxygen usually? What is its oxidation state in a peroxide? What is its oxidation state when bonded to fluorine?

A

The oxidation number of oxygen in a compound is usually -2. If, however, the oxygen is in a class of compounds called peroxides (like hydrogen peroxide), then the oxygen has n oxidation number of -1. If the oxygen is bonded to fluorine, the number is +2.

236
Q

What happens with transition metals oxidation numbers?

A

In transition metals, the oxidation number can vary.

237
Q

What are chlorine, bromine, and iodines oxidation numbers? What is the exception?

A

Chlorine, Bromine and iodine usually have numbers of -1, except when it is in a compound with oxygen.

238
Q

In compound names with roman numerals, what does the roman numeral refer to?

A

The oxidation number of the element that is joined in name to the oxygen, but not the oxygen (for example in element(1) element(2)ate (Roman Numeral) then the roman numeral refers to the element (2))

239
Q

In potassium manganate(VII), what does the VII refer to?

A

The oxidation number of manganese

240
Q

In equations, if an elements oxidation state increases what has it undergone?

A

Oxidation

241
Q

In equations, if an elements oxidation state decreases what has it undergone?

A

Reduction

242
Q

What is a disproportionation reaction?

A

when the same element is both oxidised and reduced at the same time in a reaction

243
Q

Rules for writing ionic equations

A

1) Re-write out the equation showing the separate ions present in each substance.2) Look for ions that change state and/or form non-ionic compounds and underline them3) Cross out spectator ions 4) Rewrite the equation leaving out the spectator ions. 5) Make sure your equation still balances

244
Q

How does developing chemical processes with high atom economy benefit sustainability?

A

Less environmental waste as a high percentage of atoms are being used in useful products

245
Q

Alkene general formula

A

CnH2n

246
Q

Does an alkene exist with 1 carbon?

A

no

247
Q

Are alkenes saturated or unsaturated?

A

Unsaturated

248
Q

What is the test for alkenes?

A

bromine water is decolourised (orange to colourless)

249
Q

What is a pi bond?

A

these are formed by the sideways overlap of the two adjacent p orbitals

250
Q

Chemical formula of limonene

A

C10H16

251
Q

What is limonene responsible for?

A

The smell and flavour of lemons and oranges

252
Q

What happens in an alkene addition reaction?

A

The double bond opens up and allows two atoms to join to it

253
Q

What happens in a hydrogenation of an alkene?

A

Addition reaction with hydrogen

254
Q

Conditions for hydrogenation of alkene

A

nickel catalyst and 150’C

255
Q

Why does the Z isomer have a lower boiling point?

A

It cant pack as closely together

256
Q

What happens with hydration of alkenes?

A

.Alkenes will react with steam, H2O, in the presence of phosphoric acid, H3PO4, to produce alcohols

257
Q

What does bromine water test for?

A

Unsaturation

258
Q

Why is HBr polar?

A

Br is more electronegative

259
Q

Explain how electrophilic addition works using HBr as an example

A

HBr is polar due to electronegative BrThe pi electrons attracted towards the Hs+, i.e. pi bond breaksHs+ acts as an electrophile (accepts a pair of electrons)H-Br bond breaks via heterolytic fission

260
Q

What is an electrophile?

A

‘electron loving’, able to accept a pair of electrons

261
Q

What is a nucleophile?

A

‘nucleus loving’, able to donate a pair of electrons

262
Q

Why is Br2 non-polar?

A

Both Br atoms have the same electronegativity

263
Q

How does Br2 react with an alkene?

A

Bromine is none polar due to each atom having the same electronegativityBut as bromine approaches the pi bond on the alkene, it repels the electrons in the bond and pushes them away, giving the bromine atoms slight chargesThe pi electrons induce a dipole in the non-polar Br2 molecule as it approaches the bondThis means electrophilic addition can ensue

264
Q

In electrophilic addition, in the stage between the adition of the electrophile and the addition of the other atom, what is the alkene called? Why?

A

A carbocation (or carbonium ion) as it has a positive charge

265
Q

What forms of carbocations are there?

A

Primary, secondary and tertiary

266
Q

How do +I affects increase stability?

A

Carbon centres have a positive inductive effect (+I). This pushes electron density towards the C+ and helps to stabilise it.

267
Q

The more +I effects,

A

the more stable the carbonium ion

268
Q

The more stable ions are,

A

more favourable

269
Q

Which product of electrophillic thing is more favourable?

A

Major product

270
Q

What is markownikoffs rule?

A

The major product is produced when the negative part of the molecule joins to the carbon with the least number of attached H (hydrogen) atoms within the double bond.

271
Q

What is the order of carbonium ion stability? Why?

A

Primary carbonium ions are less stable than secondary, which are less stable than tertiary, because:- Primary = 1 x +I- Secondary = 2 x +I- Tertiary = 3 x +I

272
Q

Draw the electrophillic mechanism for HCl and CH3CH=CH2

A

Check notes from 29.1.20

273
Q

Define acid

A

dissociates in water and releases H+ ions

274
Q

Define alkali

A

dissociates in water to release OH- ions

275
Q

Neutralisation equation

A

H+ + OH-1  H2O

276
Q

Bronsted Lowry Acid:

A

Proton donor

277
Q

Bronsted Lowry Base:

A

Proton acceptor

278
Q

pH = 1 (x 10 the concentration of H+ ions) pH =

A

2

279
Q

What makes an acid strong?

A

It fully dissociates

280
Q

As a Strong acid fully dissociates, pH of a strong acid can be calculated from

A

concentration of acid

281
Q

pH =

A

-log10[H+]

282
Q

Sulphuric acid is dibasic, what does this mean?

A

H2SO4  2H+ + SO42-

283
Q

[H+] =

A

10-pH

284
Q

Weak acids form an acid dissociation constant called

A

Ka

285
Q

Ka =

A

[products] / [reactants]

286
Q

[H+] = for weak acids

A

root([HA] Ka)

287
Q

[HA] is what?

A

concentration of weak acid

288
Q

How can we test for acids?

A

We can test for acids using universal indicator paper which turns red or orange depending on the strength of the acidBlue litmus paper also turns red in the presence of an acid

289
Q

HCl + H2O –>

A

H3O+ + Cl-

290
Q

What is H3O+

A

A hydronium ion, also known as an oxonium ion

291
Q

What is water acting as in the equation:HCl + H2O  H3O+ + Cl-

A

a base

292
Q

What is a bronsted-lowry base?

A

A Bronsted Lowry base is a substance which accepts protons in solution

293
Q

What is a bronsted-lowry acid?

A

A Bronsted Lowry acid is a substance which releases or donates protons in solution

294
Q

What does a bronsted-lowry acid-base reaction involve?

A

the transfer of a proton from one base to another

295
Q

What does ammonia do in water? include equation

A

Ammonia, in water, accepts a protonNH3 + H2O  NH4+ + OH-

296
Q

In the equation,NH3 + H2O  NH4+ + OH-, what is water acting as?

A

An acid

297
Q

For a bronsted-lowry base, what is the pH of an acid?

A

So for the Bronsted Lowry theory, a base does not need to have a pH>7

298
Q

What are substances that can act as either a base or an acid called?

A

Substances that can act as either an acid or a base are amphoteric

299
Q

What are some old defnitions of acids?

A

.The definition of acids has developed since the time of the ancient Greeks.Simpler ideas involved substances that had a sour taste, contained hydrogen, hydrogen ions or had a pH lower than 7

300
Q

.When a chemical reacts with an acid it is the __________ from the acid which is driving the reaction forward

A

hydrogen ion, H+,

301
Q

HCl (aq) + NaOH (aq) 

A

NaCl (aq) + H2O (l)

302
Q

How did the Bronsted-Lowry name come about?

A

Johannes Nicolaus Bronsted and Martin Thomas Lowry did not work together but both chemists formulated the idea that acids are proton donors and bases are protons acceptors

303
Q

The Brønsted–Lowry acid–base theory is a development of these earlier ideas and states that:

A

.An acid is a proton donor.A base is a proton acceptor

304
Q

.How many protons, neutrons and electrons does a Hydrogen ion, H+ have?

A

.A hydrogen ion is just a proton

305
Q

We know that HCl forms a covalent bond between the hydrogen and chlorine so what happens when it dissolves in water to become hydrochloric acid?

A

.HCl(g) + aq  H+(aq) + Cl-(aq)

306
Q

HCl(g) + aq  H+(aq) + Cl-(aq).On closer inspection is?

A

HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)

307
Q

.H3O+(aq) is known as the hydronium ion, also known as _______ ion

A

hydroxonium

308
Q

.In this equation:HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)what is HCl and H2O acting as?

A

The HCl is a proton donor (a Brønsted–Lowry acid).The H2O is a proton acceptor (a B-L base)

309
Q

In the reverse equation of HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq) what happens to the roles?

A

.In the reverse equation, the roles reverse:H3O+(aq) + Cl-(aq)  HCl(g) + H2O(l)

310
Q

once an acid has ‘donated’ a proton it would become able to ‘accept’ a proton back and hence act as a base, what is this called?

A

We call these pairs of chemicals conjugate acid-base pairs

311
Q

Give an example of a conjugate acid-base pair?

A

HCl and Cl- = Acid and conjugate base

312
Q

What are the acid base pairs in HCl + H2O H3O+ + Cl-

A

HCl = acid 1Cl- = base 1H2O = base 2H3O+ = acid 2

313
Q

What are the acid base pairs in CH3COOH + H2O CH3COO- + H3O+?

A

CH3COOH = acid 1CH3COO- = base 1H2O = base 2H3O+ = acid 2

314
Q

What are the acid base pairs in NH3 + H2O NH4+ + OH-?

A

Base 2 Acid 1 Acid2 Base 1

315
Q

What are the acid base pairs in HCO3- + HCl H2CO3 + Cl-?

A

Base 2 Acid 1 Acid 2 Base 1

316
Q

Complete the equation for the conjugate acid-base pair: CH3CH(OH)COOH + CH3CH2CH2COOH

A

CH3CH(OH)COO- + CH3CH2CH2COOH2+

317
Q

List the roles of H+ in reactions

A

spectator ions:Acid + metal  salt + hydrogenSolid carbonates and soluble carbonates:Acid + carbonate  Water + carbon dioxidebase (metal oxides): Acid + base  salt + waterAlkali: H+ + OH-  H2O

318
Q

What did Soren Sorenson do?

A

introduced simple numbers to represent the colours of indicators using an electrochemical cell to measure the hydrogen content

319
Q

What did Soren Sorenson find?

A

.He found the ion concentration had a very large range of values of powers of 10 (10-1 to 10-14)

320
Q

What is a strong acid? With general equation

A

.A strong acid is one which completely dissociates into ions in a solutionHA  H+ + A-

321
Q

So for a strong acid, [H+] =

A

concentration of the acid ([HA])

322
Q

pH =

A

-log10[H+]

323
Q

What does the equation pH = -log10[H+] tell us?

A

.It tells us the relative hydrogen ion concentration of a given solution

324
Q

What must we remember with the equation pH = -log10[H+]?

A

.THIS ONY WORKS FOR STRONG ACIDS

325
Q

.An increase in H+ x10, it reduces the pH by how much?

A

1

326
Q

What is pH of 1M HCl?

A

0

327
Q

What is Sorenson’s pH scale?

A

.The logarithmic scale means that a shift of one pH unit means a 10x change in the acidity and alkalinity of the solution.Theoretically there is no limit to the pH scale

328
Q

What type of acid is HCl, what does this mean?

A

monobasic = [H+]

329
Q

What type of acid is H2SO4, what does this mean?

A

dibasic = 2[H+]

330
Q

What type of acid is H3PO4, what does this mean?

A

tribasic = 3[H+]

331
Q

[H+] =

A

10-pH

332
Q

What is the [HCl] of a solution with pH 1.8?

A

0.016 moldm-3

333
Q

What is the [H2SO4] of a solution with pH 1.8?

A

0.008 moldm-3 as dibasic acid

334
Q

50cm^3 of 0.1M HCl is diluted to 100cm^3 with water, what is the change in pH?

A

Before dilution, pH = 10n dilution, HCl conc is halved to 0.05MAfter dilution, pH = 1.30Change = 0.3

335
Q

What is a strong acid?

A

A strong acid is one which completely dissociates into ions in a solution

336
Q

WHat does pH = -log10[H+] only work for?

A

ONLY WORKS FOR STRONG ACIDS

337
Q

[H^+] equation for changing concentraation

A

[H+] = [H+]old x (old volume / new volume)

338
Q

How are weak acids different to strong ones?

A

.Weak acids do not dissociate fully like strong acids

339
Q

What happens when a weak acid dissociates?

A

An equilibrium is established between the ions and the acid

340
Q

As an equibrlium is established when weak acids dissociate, what can we calculate?

A

we can calculate an equilibrium constant Ka (Acids dissociation cons tat)

341
Q

What does Ka equal for, HA H+ + A-?

A

Ka = ( [H+] [A-] ) / [HA]

342
Q

For the Ka equation what two assumptions need to be made?

A

.A pure acids will split evenly into equal quantities of [h+] and [A-].The concentration of the acid doesn’t change as the equilibrium lies so far to the left it can be considered equal

343
Q

does [H+] = [H+ aq]?

A

yes

344
Q

.A sample of ethanoic acid of concentration 0.04 moldm-3.What is the value of Ka?

A

2.5x10-9 moldm-3

345
Q

Steps to calculating pH of weak acid

A

.Step 1: Calculate [H+] from ka and [HA].Step 2: Calculate pH

346
Q

Are the approximations for weak acids justified?

A

.The first approximation assumes that the dissociation from water is negligible.[H+(aq)]eqm = [A-(aq)]eqm - if pH>6 then water dissociates and [H+] from water will be more significant than from dissociation of acid.This approximation breaks down for very weak acids or very dilute solutions.Second approximation assumes that the concentration of the acid [HA] is much greater than the [H+] concentration at equilibrium.[HA]start&raquo_space; [H+]eqm [HA]eqm = [HA]start – [H+]eqm so [HA]eqm = [HA]start.Not valid as acid gets stronger as [H+] becomes more significant and real difference between [HA]eqm = [HA]start – [H+]eqm.Not justified for stronger weak acids / very dilute solutions.

347
Q

.The value of Ka for weak acids is almost always very small and difficult to compare numbers with negative indices, how do we get around this?

A

create a scale of more useable numbers we often use the value of pKa, when talking about the aciditing of weak acids

348
Q

What is pKa often used for?

A

to compare acids in biological systems

349
Q

pKa equation

A

pKa = -log10Ka

350
Q

What do the values of pKa mean?

A

The higher the value of pKa, the weaker the acidThe lower the value of pKa, the stronger the acid

351
Q

How does wine show behaviour of typical dibasic and tribasic acids?

A

Wines often contain traces of sulphurous acid, H2SO3, added as a preservative.Sulphurous acid is dibasic and its dissociation is shown as:H2SO3 H+ + HSO3 - (pKa = 1.92)HSO3 - H+ + SO3 2- (pKa = 7.18).For the first dissociation, H2SO3, acts as a weak acid.From the pKa values, HSO3, is a far weaker acid than H2SO3.The behaviour is typical of dibasic and tribasic acids

352
Q

Where strong acids completely dissociate to release all H+ ions into solution, weak acids only partially dissociate, explain this in terms of equations

A

Strong: HA → H+ + A-Weak: HA ⇌ H+ + A-

353
Q

As weak acids form an equilibrium their dissociation can be represented by the acid dissociation constant, Ka, whats the equation for this?

A

Ka = “[H+(aq)][A-(aq)]” /”[HA(aq)]”

354
Q

Explain why a larger value for Ka means a lower pH

A

.The larger the value for Ka the more the equilibria lies to the right and so the lower the pH i.e. higher [H+]

355
Q

What alters Ka?

A

Temperature

356
Q

.As the values for Ka are very small it is easier to give their negative logarithm, pKa, instead, what is the equation for this?

A

pKa = - logKa

357
Q

pKa = - logKa, what is the inverse equation for this?

A

The inverse for this equation is: Ka = 10-pKa

358
Q

This means that the weaker an acid the:._____ Ka._____ pKa

A

.Smaller Ka.Larger pKa

359
Q

.The [H+] of a weak acid depends on the value of what?

A

Ka and [HA]

360
Q

.The equilibrium concentrations, [ ]eqm, can be used to determine a value for Ka, what is the equation for this?

A

Ka = “[H+]eqm [A-]eqm” /”[HA]eqm”

361
Q

There are two approximations that need to be made when calculating Ka, what are they?

A

.HA dissociation forms equal [H+] and [A-].The change in [HA] is negligible so [HA]eqm = [HA]start

362
Q

Using the approximations, Ka can be determined by what equation?

A

Ka = “[H+]eqm 2” /”[HA]start”

363
Q

How can pH be calculated for a weak acid?

A

[H+] = √(“Ka x [HA]” ) → pH = -log[H+]

364
Q

.A value for Ka can be determined experimentally, how?

A

by using a pH meter to get the pH of a standard solution

365
Q

.The larger the value for Ka, the greater the _________

A

dissociation

366
Q

When calculating values for Ka there are issues with the approximations made, what are these issues?

A

• At pH values >6 water dissociation is significantTherefore doesn’t work for very weak acids or very dilute solutions• If [H+] concentration is significant there will be a difference between [HA]eqm and [HA]startTherefore doesn’t work stronger weak acids with Ka > 10-2 mol dm-3 or very dilute solutions

367
Q

All aqueous solutions contain which ions?

A

H+ and OH- ions

368
Q

H2O

A

H+ + OH-

369
Q

In ____ [H+] > [OH-]In ____ [OH-] > [H+]In ____ [H+] = [OH-]

A

In acids [H+] > [OH-]In alkalis [OH-] > [H+]Neutral [H+] = [OH-]

370
Q

For every 500,000,000 H2O molecules, only _ dissociates

A

1

371
Q

For every 500,000,000 H2O molecules, only 1 dissociates, what does this mean for the equilbrium?

A

the equilibrium is on the left hand side

372
Q

Do the Kc equation for water equilibrium

A

Kc = ([H+][OH-]) / [H2O]

373
Q

[H2O] x Kc =

A

[H+] x [OH-]

374
Q

[H2O] is such a large excess it can be classed as a ____

A

constant

375
Q

What is Kw?

A

ionic product of water

376
Q

Kw = [H2O] x Kc, so replace [H2O] x Kc with Kw in the correct equation

A

Kw = [H+] x [OH-]

377
Q

At 298K, Kw =

A

1x10-14 mol2dm-6

378
Q

Why is the pH of pure water at 298K, 7?

A

Kw = [H+] x [OH-]1x10-14 = [H+] x [OH-]The concentrations are the same and so it can be written as:1x10-14 = [H+]21x10-7 = [H+]pH = 7

379
Q

Effect of temperature on Kw

A

The dissociation of water is endothermicTemperature increase will move the equilibrium to the right, and so Kw will increaseTemperature decrease will move the equilibrium to the left, and so Kw will decreaseWater will always remain neutral at all temperatures, pH may change with temperature, but [H+] = [OH-] all the time and so it is neutral

380
Q

.Water ionises very slightly, acting as both an acid and as a base – setting up an ________

A

equilibrium

381
Q

.Water dissociates a very, very small amount according to the equation – it must do, otherwise it would not _____________

A

conduct electricity

382
Q

.1 dm3 (1000g) of water is mainly ________ H2O

A

undissociated

383
Q

. [H2O(l)] = 1000/18 = 55.6 mol dm-3 (a constant), why?

A

.1 dm3 (1000g) of water is mainly undissociated H2O

384
Q

.If we know the concentration of hydroxide ions we can rearrange Kw to give us the value of what?

A

[H+]

385
Q

What is the pH of 0.4 mol dm-3 NaOH?

A

Kw = [H+][OH-] = 1.00 × 10–14 mol2dm–6 (1.00 × 10_14 )/([0.4])=[H+] = 2.5 x 10-14 mol dm-3 pH = -log10[H+] = -log10[2.5 x 10-14 ] = 13.60

386
Q

What is the pH of a solution with [OH-] = 2 x 10-2 mol dm-3 at 25oC ?

A

Step 1 : calculate [H+] from Kw and [OH-] Kw = [H+][OH-] = 1.00 x 10-14 [H+] = Kw = 1.00 x 10-14 = 5.00 x 10-13 mol dm-3 [OH-] 2.00 x 10-2Step 2 : Use calculator to find pH pH = - log [H+] = -log (5.00 x 10-13) = 12.30

387
Q

What are the concentrations of H+ (aq) and OH- (aq) in a solution of pH 3.25 at 25oC ?

A

Step 1 : Use calculator to find [H+(aq)][H+] = 10-pH = 10-3.25 = 5.62 x 10-4 mol dm-3Step 2 : Calculate [OH-] from Kw and [H+]Kw = [H+][OH-] = 1.00 x 10-14[OH-] = Kw = 1.00 x 10-14 = 1.78 x 10-11 mol dm-3 [H+] 5.62 x 10-4

388
Q

For pH values that are whole numbers, it is easy to work out the [H+] and [OH-] concentrations as the indices add up to what?

A

-14

389
Q

.The pH of weak bases can be calculated via a similar method to that used for ______

A

weak bases

390
Q

.In an aqueous solution, there will always be both H+ (aq) and OH- (aq) ions present such that ________

A

[H+ (aq)][OH- (aq)] = Kw

391
Q

.A solution is ______ when [H+ (aq)] > [OH- (aq)] .A solution is ______ when [H+ (aq)] = [OH- (aq)].A solution is ______ when [OH- (aq)] > [H+ (aq)]

A

.A solution is acidic when [H+ (aq)] > [OH- (aq)] .A solution is neutral when [H+ (aq)] = [OH- (aq)].A solution is alkaline when [OH- (aq)] > [H+ (aq)]

392
Q

.So a solution that is acidic will still contain __ ions, it is just that there are more __ions (and vice versa in an ______ solution)

A

OH-H+Alkaline

393
Q

.The value of Kw controls the ______ of each ion

A

Concentrations

394
Q

• Kw can also tell us the pH of ______

A

pure water

395
Q

• As the water splits into equal concentrations of OH- and H+ ions we can make what assumption?

A

Kw = [H+][OH-] = 1.00 × 10–14 mol2dm–6 = [H+]2 = 1.00 × 10–14 = [H+] = 1.00 × 10–7 pH = -log10[H+] = -log10[1.00 x 10-7 ] = 7

396
Q

When is neutral not neutral?

A

.A neutral solution is defined by a equal number of moles of H+ ions and OH- NOT by a pH of 7 as you may have been taught.Whilst this value is 7 at approximately 298K, the value of Kw increases with temperature

397
Q

.The pOH scale measures what?

A

the concentration of hydroxide ions

398
Q

.Therefore you can solve fpr pH, pOH and [OH-] given just ___

A

[H+]

399
Q

pH + pOH =

A

14

400
Q

.Kw = [H+][OH-] =

A

1x10-14

401
Q

H2O(l) H+(aq) + -OH(aq)

A

Water slightly ionises, what equation will show this?

402
Q

[H+][-OH] / [H2O]`

A

Ka of :H2O(l) H+(aq) + -OH(aq)=

403
Q

Kw

A

Ka x [H2O] =

404
Q

[H+][-OH]

A

Kw =

405
Q

Kw is the ionic product of water, at 25’C it equals 1x10-14 mol2dm-6

A

What is Kw?

406
Q

What is a buffer?

A

a solution that minimises pH change when a small amount of acid or alkali is added

407
Q

What two types of buffers are they?

A

Weak Acid and Salt of Weak AcidExcess Weak Acid and Strong Base

408
Q

Suggest and explain a Weak Acid and Salt of Weak Acid buffer

A

Weak Acid – Ethanoic Acid – CH3COOH(aq) CH3COO-(aq) + H+(aq)Salt of Weak Acid – Sodium Ethanoate – CH3COONa(s) + (aq) CH3COO-(aq) + Na+(aq)¬Buffer Contains – CH3COOH(aq) CH3COO-(aq) + H+(aq)When add H+, H+ reacts with conjugate base, equilibrium will move to the left to reduce the amount of H+, pH is constantAdding –OH (alkali) –-OH + H+  H2OConc of H+ decreases, equilibrium moves to the right to increase the conc of H+, pH is constant

409
Q

Suggest and explain an excess Weak Acid and strong base buffer

A

CH3COOH(aq) + NaOH(aq) –> CH3COONa(aq) + H2O(l)CH3COONa(aq) CH3COO-(aq) + Na+(aq)CH3COOH(aq) CH3COO-(aq) + H+(aq)When add H+, H+ reacts with conjugate base, equilibrium will move to the left to reduce the amount of H+, pH is constantAdding –OH (alkali) –-OH + H+  H2OConc of H+ decreases, equilibrium moves to the right to increase the conc of H+, pH is constant

410
Q

Excess methanoic acid is reacted with potassium hydroxide, explain how a buffer solution is produced and how pH is controlled when 5cm3 of HCl is added.

A

The solution now contains HCOOK(aq) HCOO- (aq) + K+(aq) and HCOOH(aq) HCOO-(aq) + H+ equilibriums in solution – the buffer. When 5cm3 of HCl is added, it dissociates into H+ and Cl-, the H+ ions increase the concentration of the H+ already in the solution, so the HCOOH(aq) HCOO-(aq) + H+ point of equilibrium moves to the right – decreasing the conc of H+ in solution, and so keeping the pH constant.

411
Q

Ka x ( [HA]/[A-] ) = ? what does each part mean?

A

[H+] = Ka x ( [HA]/[A-] )[HA] = concentration of weak acid[A-] = concentration of conjugate base

412
Q

50cm3 of 1.2M NaOH reacts with 250cm3 of ethanoic acid (1M), Ka = 1.74x10-5, what is the pH?

A

CH3COOH CH3OO- + H+CH3COOH + NaOH  CH3COO- + Na+ + H2O1. Moles weak acid = 250x1 / 1000 = 0.25mol2. Moles NaOH = 50x1.2 / 1000 = 0.06mol3. Moles A- = 0.06mol4. Moles HA = 0.19mol5. [H+] = Ka ([HA] / [A-]) = 1.74x10-5 x (0.19/0.06) = 5.51x10-56. pH = 4.26

413
Q

Blood must contain a pH of what?

A

Blood must contain a pH of 7.40 +- 0.05

414
Q

What is the most important buffer in blood?

A

the carbonic acid – hydrogencarbonate

415
Q

Carbonic acid dissociation equation

A

H2CO3 H+ + HCO3-

416
Q

If blood becomes too acidic (acidosis), what presents?

A

fatigue, shortness of breath, shock, death

417
Q

If blood becomes too alkaline (alkalosis), what presents?

A

spasms, light-headed, nausea

418
Q

What happens if the body produces more acidic products?

A

.The H+ concentration in the blood will increase, the equilibrium of the hydrogencarbonate dissociation will shift to the left, the H+ ions will be used up to form more hydrogencarbonate, the H+ concentration will return to normal, the pH will have had minimal change.If the acid level continued to rise, fatigue, shortness of breath, shock, or death would eventually set in.This would occur when we have ran out of HCO3- ions

419
Q

Carbon dioxide dissolves in water to form what? What is the equation for this?

A

carbonic acid:CO2 + H2O H2CO3

420
Q

Inhalation of high levels of CO2 means what?

A

Inhalation of high levels of CO2 mean that the equilibrium in the blood must shift to the right to form more H2CO3, this means that the level of H2CO3 in the blood increase, so in the equilibrium H2CO3 H+ + HCO3- the equilibrium shifts to the right to counter this, this forms more H+ ions in the blood, making it more acidic, and resulting in acidosis which would lead to fatigue, shortness of breath, shock, and eventual death. Increased [H+] means enzymes would also be denatured.

421
Q

Draw the titration curve for when HCl is added to NaOH

A

check notes

422
Q

Draw the titration curve for when NaOH is added to HCl

A

check notes

423
Q

Draw strong acid strong base titration curve

A

check notes

424
Q

Draw strong acid weak base titration curve

A

check notes

425
Q

Draw weak acid strong base titration curve

A

check notes

426
Q

Draw weak acid weak base titration curve

A

check notes

427
Q

The shape of the titration curve depends on what?

A
  • Substance being titrated i.e. acid or base- Type of acid or base i.e. strong or weak
428
Q

Describe and explain parts of titration curve

A
  1. Excess of base: pH decreases as acid added2. Vertical section: acid base concentration similar, pH alters rapidly3. Excess of acid: pH decreases slightly as acid is added4. The equivalence point: halfway up the vertical section
429
Q

What is the equivalence point?

A

The point halfway between the two horizontal lines on the titration curveThe equivalence point is the volume required to have completely reacted the acid and base toetehr, stoichiometric volumesThe pH at the equivalence point depend son the type of acid and base

430
Q

Where is the equivalence point on each titration curve?

A

Equivalence point = 7 on SA-SBEquivalence point < 7 on SA-WBEquivalence point > 7 on WA-SBNo equivalence point on WA-WB

431
Q

Why is the equivalence point 0 on SASB titration curves?

A
  • H+ ions completely neutralised by OH- ions, so only water and salt present, neutral
432
Q

Why is the equivalence point < 7 on SAWB titration curves?

A
  • A weak base, like NH3, will have a strong conjugate acid, NH4+ , which will react with water to produce H3O+ so the pH is less than 7
433
Q

Why is the equivalence point > 7 on WASB titration curves?

A
  • A weak acid, HA, will have a strong conjugate base, A-, which can react with water to produce OH- ions, so the pH is more than 7
434
Q

What are acid-base indicators?

A

Acid-Base indicators are weak acids that have different coloured conjugate basesIn acidic conditions the indicator equilibrium is shifted towards the weak acid (HIn)As the system becomes more basic the equilibrium shifts towards the conjugate base (In-), altering the colour

435
Q

What is the end point?

A

The end point is when equal [HIn] and [In-] are present, the colour will therefore lie between both extremesEach indicator will have a different pH value for the end point as they each have different ka values

436
Q

HIn

A

H+ + In-

437
Q

How is an acid-base indicator chosen?

A

The indicator required for a titration must have a colour change that lies within the vertical section of a titration curve

438
Q

Draw an aldehyde group

A

google it

439
Q

Draw an ester group

A

google it

440
Q

Draw a haloalkane group

A

google it

441
Q

Draw an alcohol group

A

google it

442
Q

Draw an alkene group

A

google it

443
Q

Draw a carboxylic acid group

A

google it

444
Q

Draw a ketone group

A

google it

445
Q

Draw an amine group

A

google it

446
Q

What are aromatic hydrocarbons?

A

Aromatic hydrocarbons are when some or all of the carbons are found in a benzene ring

447
Q

What are aromatic hydrocarbons also called?

A

Arenes

448
Q

What is an alkyl group?

A

An alkyl group has a hydrogen group removed from the alkane chain

449
Q

What are compounds with one substituent group?

A

.These are aromatic compounds with one substituent group that is mono-substituted on to a benzene ring

450
Q

.If the substituent group is: An alkyl group (e.g. CH3), halogen (e.g. Br, Cl), or a nitro group (NO2).Then …

A

the parent group is classed as the benzene ring and the group added is considered the prefix

451
Q

If the substituent group is: amine or an alcohol, then …

A

the parent group is classed as the functional group and benzene is classed as the prefix

452
Q

What is the prefix for benzene?

A

phenyl

453
Q

Draw Benzene carboxylic acid

A

google it or check notes

454
Q

Draw Benzaldehyde

A

google it or check notes

455
Q

Some molecules may contain more than one substituent group, so it may have ___ substituents bonded to it.

A

two

456
Q

We number the benzene ring like you would a ____ chain

A

carbon

457
Q

The substituent groups are listed in _____ order and using the ________ possible number.

A

alphabetical smallest

458
Q

Draw 2-chloro methylbenzene

A

google it or check notes

459
Q

Draw 3-methylphenylamine

A

google it or check notes

460
Q

When was Benzene discovered? and by who?

A

Discovered in 1825 by Michael Faraday

461
Q

what is the percentage make up of benzene found by faraday? relative formula mass, and empirical formula

A

.92% carbon, 8% hydrogen.It has a relative formula mass of 78.Empirical formula found to be CH

462
Q

What was weird about benzene when discovered?

A

.The structure was difficult to define

463
Q

Who proposed the first structure of Benzene, what was it and did it work?

A

.Kekule’s proposed structure for benzene.It was planar, cyclic with alternating double and single bonds which had 120’ bond angles.But there were problems with this structure

464
Q

What was the chemical evidence against Kekule’s benzene?

A

.Benzene would not react with bromine, hydrogen bromide, and sulfuric acid.This tells us there are no double bonds in the molecule.The molecule does not undergo electrophilic addition reactions

465
Q

What was the bond length evidence against Kekule’s benzene?

A

.A carbon-carbon single bond length is 0.153nm.A carbon-carbon double bond length is 0.134nm.So you would expect benzene to be an irregular hexagon.In 1922, Kathleen Lonsdale used x-ray diffraction to measure the bond length in benzene.She found it had a regular shape.She found that all the carbon-carbon bonds were the same length – 0.14nm.Each bond is an intermediate between a single and double bond

466
Q

What was the thermochemical evidence against Kekule’s benzene?

A

.The enthalpy of hydrogenation is defined as the change in enthalpy when 1 mole of unsaturated compound reacts with an excess of hydrogen to become fully saturated.The molecule had an enthalpy of -208, Kekule’s model in theory should have had -360.So it’s bonds are more stable than cycloalkenes, as it is less exothermic than expected

467
Q

Describe the declocalised model of benzene

A

.Each carbon atom has 3 σ (normal) bonds.This leaves a spare electron in 2p orbital.120’ bond angle between carbon atoms.Planar hexagonal molecule.2p orbitals overlap above and below the ring.To form pi bonds.The electrons in the pi bonds are delocalised

468
Q

Draw the delocalised model of bezene

A

check notes or google

469
Q

Draw Kekule’s benzene model

A

Check notes or google

470
Q

What is an electrophile?

A

An electrophile is an electron acceptor and can have a positive charge

471
Q

What must an electrophile have to attack the stable benzene ring?

A

An electrophile has to have a strong positive charge to be able to attack the stable benzene ring, most compounds just aren’t polar enough

472
Q

What does an electrophile need when attacking a benzene ring?

A

Needs a halogen carrier – iron, iron halides (e.g. FeCl3) or aluminium halides (e.g. AlCl3)

473
Q

Br-Br: + AlBr3 

A

AlBr4- + Br+

474
Q

In an electrophilic substitution reaction with benzene, what does the halogen carrier do?

A

The halogen carrier accepts a lone pair of electrons from a halogen atom, as the lone pair is pulled away from the polarisation increases forming a strong electrophile

475
Q

What is halogenation?

A

when a hydrogen atom is substituted for a halogen on a benzene ring

476
Q

Give an example of halogenation

A

bromine is substituted onto a benzene ring to make bromobenzeneC6¬H6 + Br2  AlBr3  C6H5Br + HBr

477
Q

WHat is the mechanism to a halogenation?

A

Step 1 – creating the electrophile with the halogen carrier catalystStep 2 – electrophile accepts a long pair of electrons from the benzene ring to form a dative covalent bond, this forms as unstable intermediate, the intermediate breaks down to form the organic productStep 3 – the catalyst is regenerated

478
Q

Draw the halogenation of benzene with Br2 with the AlBr3 catalyst

A

check notes or google

479
Q

Benzene reacts with nitric acid at what speed?

A

slowly

480
Q

How can we increase the rate of reaction of benzene and nitric acid?

A

by using sulphuric acid as a catalyst and 50’C

481
Q

What happens when benzene reacts with nitric acid?

A

The H atom is substituted for a nitro (NO2) group

482
Q

C6H6 + HNO3  H2SO4 

A

C6H5NO2 + H2O

483
Q

Draw the mechanism for benzene and nitric acid

A

check notes or google

484
Q

Describe the steps of the mechanism for benzene and nitric acid

A

Step 1: Creating the electrophile with the sulphuric acidStep 2: Electrophile accepts a lone pair of electrons from the benzene ring to form a dative covalent bond, this forms an unstable intermediate – the intermediate breaks down to form the organic productStep 3: The catalyst is regenerated

485
Q

Why is the reaction between benzene and nitric acid kept at 50’C?

A

so that only 1 nitro group attaches

486
Q

What is alkylation?

A

.This is when a hydrogen atom is substituted for an alkyl group on a benzene ring.Called the Friedel crafts reaction

487
Q

In alkylation, what does the alkyl group need to be attached to?

A

a halogen

488
Q

Give an example of alkylation

A

a methyl group is substituted onto a benzene ring to make methyl benzene

489
Q

For alkylation, the halogen in the catalyst has to be what?

A

the same as the halogen the alkyl group is attached to

490
Q

Draw the mechanism for attaching a methyl group to benzene

A

Check notes

491
Q

What is Acylation?

A

.This is when a hydrogen atom is substituted for an acyl chloride group on a benzene ring.Also called the Friedel crafts reaction

492
Q

Draw the acyl chloride group?

A

check notes or google it

493
Q

In an acylation reaction, Ethanoyl chloride reacts with benzene to make what?

A

phenylethanone

494
Q

Draw the mechanism for benzene becoming phenylthanone

A

check notes

495
Q

What are phenols?

A

Phenols are a type of organic chemical containing a hydroxyl group (-OH) functional group directly bonded to an aromatic ring

496
Q

The simplest member of the phenols is ?

A

Phenol

497
Q

Draw phenol

A

check notes or google

498
Q

.Any compound that has an OH (hydroxyl) group bonded directly to a benzene ring is a what?

A

phenol

499
Q

.If the compound doesn’t have a OH bond directly but still has an OH group it is classed as an ______, not a ______

A

alcohol, not a phenol

500
Q

.Phenol is less soluble in water than alcohols, why?

A

due to its non-polar benzene ring

OCR A Level Chemistry (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions