Unit 1 And 2 Flashcards
1
Q
What is the equation for heat energy?
A
E = cm(delta)T
This value can be scaled up or down according to the mass of the substance in order to calculate the enthalpy.
2
Q
Using collision theory, explain why surface area impacts reaction rates
A
More surface area = more chances of successful collisions
3
Q
What is an endothermic reaction?
A
A reaction that takes in heat energy. The enthalpy value is positive, reactions may incur costs in supplying sufficient heat energy.
4
Q
What does it mean by a self-indicating reaction?
A
A reaction in which the colour change occurs naturally. For example, purple permanganate solution turns colourless when reduced.
5
Q
Why might a reaction not be 100% efficient?
A
- large amounts of waste products
- spillages
- inaccurate measurements
- incomplete reaction
6
Q
Why are there no electronegativity values for noble gases?
A
Noble gases have a full outer shell and do not make compounds.
7
Q
How do ions move?
A
They move through solution or ion bridges.
8
Q
How do electrons flow?
A
They move through wires, from most reactive to least reactive metal.
9
Q
What is an ionic bond?
A
The electrostatic force of attraction between positively and negatively charged partcles.
10
Q
What is a reducing agent?
A
A chemical which causes reduction, it oxidises itself by losing electrons.
11
Q
What is an oxidising agent?
A
A chemical that causes oxidation, it reduces itself by gaining electrons.
12
Q
Why are symmetrical molecules with polar covalent bonds overall non-polar?
A
- The polarity of the bonds cancels out
- No permanent dipoles
- Only force present is LDFs
13
Q
Which of the first 20 elements are covalent molecular?
A
H², N², O², F², Cl², P⁴, S⁸ and fullerene/C60
Numbers are suppost to be at bottom of the letter
14
Q
Which of the first 20 elements are metallic?
A
Li, Be, Na, Mg, Al, K, Ca.
15
Q
What happens to covalent radius going down a group?
A
More electrons shells = atomic radius increases
16
Q
What is a covalent bond?
A
Strong forces of attraction between a positive nuclei and negative shared pair of electrons.
17
Q
What is the relationship between melting point/boiling point and the type of intermolecular force?
A
The stronger the intermolecular force, the higher the melting and boiling point.
18
Q
What is the covalent radius?
A
The concalent radius is half the distance between two nuclei in a bond.
19
Q
What does the periodic table allow chemists to predict?
A
The physical properties and chemical behaviour for any element.
20
Q
What is the equation for enthalpy change in a reaction pathway?
A
(Delta)H = Hp - Hr
21
Q
What is the Bonding continuum?
A
Pure covalent polar convalent
|———‐—————|—————————-
Ionic
–|—————|
= Increasing difference in electronegativity from left to right
22
Q
What is feedstock?
A
A chemical derived from raw materials used to make other chemicals.
E.g. ethene, aluminium, chlorine
23
Q
What are the possible places of errors when calculating enthalpy of combustion?
A
- heat loss to the surroundings
- incomplete combustion
- evaporation of alcohol vapours
24
Q
What is a limiting reagent?
A
The reactant which gets completely used up in chemical reactions. The other reactant(s) are said to be in excess.
25
What does Hess Law state?
The total enthalpy change during the complete course of a chemical reaction is the same whether the reaction is made in one step or several.
26
How do you write equations with complex ions?
1. Write the start and end ions
2. Balance the non-oxygen ions
3. Balance O² with H²O molecules
4. Balance H² with H+ ions
5. Balance charge with e-
27
What happens to ionisation energy going across a period?
Number of protons increases = outermost electron is held more tightly by increasing nuclear charge = ionisation energy increases
28
What happens to electronegativity going across s period?
Crossing a period = more protons = outer electrons pulled closer to the nucleus = electronegativity increases
29
What happens to ionisation energy when going down a group?
Going down a group = outermost electrons are further away from the nucleus due to longer number of shells = screening effect from inner electrons = electrons are easier to remove = 1st ionisation energy decrease
30
How does the size of the ion present impact its melting and boiling point?
The bigger the ion = the weaker the electrostatic attraction = melting point is lower
31
What happens to electronegativity going down a group?
Going down a group = more electron shells = screening effect from inner electrons = weaker pull from the nucleus = electronegativity decreases
32
Using collision theroy, explain how concentration impacts reaction rate.
More particles = more collisions = more chances of successful collisions.
As the reaction rate progresses, reactants get used up, less possible collisions, rate decreases.
33
What are LDFs?
London Dispersions Forces
* weak intermolecular/interatomic forces
* caused by the electron wobble
* temporary dipoles
They exist between all atoms.
34
What is the relationship between volatility and size of the molecule?
Bigger molecular size = more intermolecular forces = less volatile
35
What are the properties of metals?
* high melting and boiling points
* conduct heat and electricity
* ductile
* malleable
36
What happens to the boiling points as we go down the group of noble gases?
Going down a group = more electrons = bigger induced dipole = stronger LDFs = higher boiling points
37
What is the second ionisation energy?
The energy required to remove one mole of electrons from one mole of 1+ ions in the gaseous state.
38
What is the first ionisation energy?
The energy required to remove one mole of electrons from one mole of atoms in the gaseous state.
39
What is a hydrogen bond?
* weak intermolecular force
* stronger permanent dipoles
* caused by a difference in electronegativity of atoms
* when a Hydrogen atom of one molecule attaches to an F, O, N atom in another molecule
* because F, O, N have higher electronegativity values
40
What type of agents do elements with high electronegativity act as?
Oxidising agents
| They tend to form ions by gaining electrons
41
How can the peak area be reduced in a chromatography?
* dilute samples (reduce concentration)
| * inject less of the sample
42
How do you make a standard solution?
* dissolve the solute (in a small volume of water)
* transfer to volumetric flask while rinsing
* fill to the line of the volumetric flask
43
Using collision theory, explain why temperature impacts reaction rates.
Higher temperature = more energy = faster movement = more successful collisions
44
What are the environmental considerations of industrial processes?
* minimising waste
* avoiding the use/production of toxic substances
* designing products which will biodegrade if appropriate
45
What are the properties of graphite?
* conductor due to demoralised electrons
* atoms in layers
* brittle
46
What are the properties of diamond?
* diamond
* atoms arranged in 3D (tetrahedral)
* strong
47
What is electronegativity?
A measure of the attraction of an atom involved in a bond has for the electrons of the bond.
48
What is the effect of the neutralisation on Equilibrium?
Adding an acid = increase in H+ ions: ethier increases the concentration of H+ or the ions will react with OH- ions using them up.
And vice versa for adding an alkali.
49
What is the relationship between retention time and mass?
The larger the mass the longer the retention time
50
What is atom economy?
A measure of the proportion of reactant materials found in the desired product.
51
What is an Equilibrium?
Where the rates of the forward and reverse reaction are equal.
The concentrations of reactants and products are constant but not always the same.
52
What measurements need to be taken when calculating enthalpy of combustion?
* volume of water
* temperature of water at the start
* temperature of water at the end
* mass of the alcohol at the start
* mass of the alcohol at the end
53
What is the relationship between viscosity and type of intermolecular force?
The stronger the intermolecular force = more viscous
54
What is percentage yield?
A measure of how efficient a reaction is (ie. A measure of the degree to which a limiting reagent is converted into desired product).
55
What is enthalpy?
A measure of the chemical energy in a substance.
56
What is a Redox reaction?
A reaction in which reduction and oxidation take place at the same time.
57
How can viscosity be measured?
A ball bearing could be dropped in the liquids, the longer it takes to reach the bottom the more viscous.
58
What is the activation energy (Ea)?
The minimum energy required by colliding particles to form an activated complex. The Ea can be calculated from potential energy diagrams.
59
Why do reaction rates need to be controlled in an industrial process?
Rate too low => not economically viable
Rate too high => risk of explosion
60
When do ionic compounds conduct?
When molten or in solution because the ions are free to move.
61
Which group in the periodic table are the strongest oxidising agents?
Group 7
62
How do polar compounds behave in electric fields?
They will be attracted to other charged objects.
63
How can the solubility of a compound be predicted?
'Like' dissolves 'Like'
ie. polar substances dissolve well in water (a polar molecule)
64
What are examples of reducing agents?
CO gas is a good reducing agent. Metals are extracted from ores in reduction reactions.
65
What group in the periodic table are the strongest reducing agents?
Group 1
66
What type of agent are elements with low electronegativity?
Acts as a reducing agents (they to form ions by losing electrons)
67
What are examples of oxidising agents?
H⁸O² - bleaching agent
KMnO⁴ - treatment of fungal infections
Oxidising agents are widely used to kill fungi/bacteria and inactive viruses.
68
What is the molar bond enthalpy?
The energy required to break one mole of bonds in a diatonic molecule.
69
What is a titration?
Titrations are used to determine, accurately, the volumes of solution required to reach the end - point of a chemical reaction.
70
What is the mean bond enthalpy?
The average energy required to break one mole of bonds, for a bond that occurs in a number of compounds.
71
What is chromatography?
A technique used to separate the components present within a mixture.
Chromatography separates substances by making use of differences in their polarity or molecular size.
72
What is temperature?
A measure of the average kinetic energy of the particles in substance.
73
What are bond enthalpies used for?
To estimate the enthalpy change occurring for a gas phase reaction.
Bond breaking = endo +
Bond making = exo -
74
How do you measure Rf?
Rf = distance travelled by component / distance travelled by solvent
75
What is the activated complex?
An unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction.
This is where the reactants bonds start to break and products start being made.
76
What is a raw material?
A substance that is removed from the planet and processed/converted to make the feedstock.
E.g. crude oil, metal ores, water, salt
77
What is the structure of an ionic compound?
A lattice structure of positively and negatively charged ions.
78
Why is the 2nd ionisation energy much higher for alkali metals?
The second mole of electrons has to be removed for a full outer shell.
79
What is the effect of temperature on Equilibrium?
An increase in temperature favours exothermic reactions.
80
What is the effect of pressure on Equilibrium?
Pressure only affects substances in the gaseous state. Increase in pressure causes Equilibrium to shift to the side with less moles of gas.
81
What is a monotonic elements?
They exist as single atoms and contain no intermolecular forces.
82
Why is the density of ice less than that of water a low temperatures?
Hydrogen bonding between molecules in ice results in an expanded structure.
83
How is a polar convalent bond formed?
Difference in electronegativity of atoms form permanent dipoles.
84
What does the ionic formulae tell us?
The simplest ratio of each type of ion in the substance.
85
Why do LDFs have significant effect in monatomic substances?
It is the only type of force present
86
What are permanent dipoles?
* weak intermolecular forces
* caused by the difference of electronegativities of atoms
* polar molecules
87
What is the equation for atom economy?
Atom economy % = mass of desired product / total mass of reactants × 100
88
What is the effect of concentration on Equilibrium?
Increase in the concentration of one substance causes Equilibrium to shift to the opposite side from that substance to use it up.
89
Using collision theory, explain how pressure impacts reaction rate
Higher pressure = smaller space = more collisions = more successfull collisions
90
What happens to convalent radius going across periods?
Number of protons increases = electrons are pulled closer to the nucleus = atomic radius decreases
91
Which of the first 20 elements are a concvalent network?
B, Si, C (in the form of graphite and diamond)
92
What is a a metallic bond?
The electrostatic force of attraction between positive metal ions and delocalised electrons
93
What is the effect of catalysts on Equilibrium?
A catalyst speeds up the reaction in both directions and therefore does not alter the position of the Equilibrium pr yield of product but does decrease the time taken to reach Equilibrium.
The catalyst reacts for a small time.
94
Which of the first 20 elements are monoatomic?
He, Neil, Ar
95
What is the relationship between volatility and type of intermolecular force?
Weaker intermolecular force = more volatile
96
Why do paperclips pr water striders ect. float?
Water has a high surface tension, the molecules on the surface have, in effect, hydrogen bonds. This has the effect of pulling the surface molecules closer together.
97
Hoe to answer Hess Law calculations?
1. Write target equation
2. Find chemicals in other equations
3. If chemical is on the same side of equation as the target, enthalpy symbol stays the same.
4. If chemical is in different side, enthalpy symbol flips.
5. Scale up if different number of moles
98
What are the 2 requirements for particles to collide with each other?
* collisions have enough energy (above the activation energy)
* correct orientation/geometry
99
Why is an acid added to a reaction?
To provide H+ ions
100
What are the 5 ways to increase the rate of the reaction?
* increase surface area
* increase concentration
* increase temperature
* increase pressure
* add a catalyst
101
Why is an indicator normally used for titrations?
To show when the end point is reached
102
What is a standard solution?
A solution of exact known concentration
103
Why is universal indicator never used in titrations?
There is no sudden colour change
104
What is an exothermic reaction?
A reaction relaeses heat energy, the enthalpy value is negative. Reactions may require this heat to be removed.
105
What is a reduction reaction?
Gain of electrons
106
What is an oxidation reaction?
Loss of electrons
107
What are the strongest oxidising agents on the electrochemical series?
Bottom of the left hand column
108
Where are the strongest reducing agents on the electrochemical series?
Top of the right hand column
109
What is it called when the volumes are within 0.2cm³?
Concordant
110
What is the effect of adding chemicals not present in the Equilibrium?
These chemicals will react with other chemicals present in the Equilibrium using them up. Equilibrium shifts to the side with the chemical to make more.
111
What are the two types of catalyst?
Heterogenous - reactants and catalyst in different states
Homogenous - reactants in the same state as catalyst
112
What happens to the strength of a metallic bond going across a period?
Going across a period = more outer electrons = more delocalised electrons = stronger metallic bonds
113
What is the equation for relative rate?
Relative rate = 1 / reaction time
114
How can you identify a component using chromatography?
* the distance it has travelled
| * the time taken to travel through the apparatus (retention time)
115
What is the molar volume?
The volume occupied by 1 mole of gas at a certain pressure and temperature.
The molar volume is the same for all gasses at the same pressure and temperature.
116
What is volumetric analysis?
Using a solution of accurately known concentration in a quatative reaction to determine the concentration of another substance.
117
What are the factors influencing industrial process design?
* avaliablitly, sustainability and cost of feedstock
* opportunities for recycling
* energy requirements
* marketability of by-products
* product yield
118
What is the enthalpy of combustion?
The enthalpy change when one mile of a substance burns completely in oxygen
