Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry > Unit 2 Questions > Flashcards

Unit 2 Questions Flashcards

1
Q

What is the definition of enthalpy?

A

The heat content of a system at constant pressure.

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

In an exothermic reaction, is the H of the products or reactants bigger and why?

A

The H of the reactants is bigger because it has a negative deltaH.

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

What is the standard temperature in degrees celcius?

A

25 degrees

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

Give the definition of the standard enthalpy change of formation.

A

The enthalpy change when one mole of a substance is formed from its constituent elements in their standard states under standard conditions.

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

Give the definition of the standard enthalpy change of combustion.

A

The enthalpy change when one mole of a substance is completely combusted in oxygen under standard conditions.

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

State Hess’s law

A

The total enthalpy change for a reaction is independent of the route taken from reactants to products.

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

You got this!

A

You’re doing so well!! :)

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

What is the definition of bond enthalpy?

A

The enthalpy needed to break a covalent X-Y bond into X atoms and Y atoms all in the gas phase.

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

What is the average bond enthalpy?

A

The average enthalpy needed to break a certain type of covalent bond of a gaseous species.

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

Why is there a difference between bond enthalpy and average bond enthalpy?

A

Because the bond enthalpy varies depending on the structure of the rest of the molecule.

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

Is breaking bonds exothermic or endothermic?

A

Endothermic because it needs energy.

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

Which equation gives you Q?

A

Q=mc/\t where /\ is my rubbish delta :)

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

Which equation gives you /\H?

A

/\H = -Q/n

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

State the full equation for working out /\H.

A

/\H = -(mc/\t)/n

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

Which two practicals can be used to indirectly determine /\H?

A

Calorimeter and combustion of fuel.

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

Define the rate of reaction

A

The change in concentration of a product or reactant per unit time.

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

Explain briefly the relationship between rate and concentration of reactants.

A

Reactant concentration high at start => rate high at start.
Reactant concentration decreases => rate decreases.
Reactant concentration reaches zero => rate drops to zero.

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

How do you calculate the rate at any point from a graph?

A

Draw a tangent and work out the gradient.

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

Which experiment would you use to find the relationship between initial rate and initial concentration?

A

A series of experiments where one reactant is changed at a time.

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

Give the four factors affecting rate

A
  1. Concentration of solution (pressure of gas)
  2. Surface area of solid
  3. Temperature of reaction
  4. Light (only in reactions like photosynthesis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define activation energy

A

The minimum energy needed to break a covalent bond and start a reaction.

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

What are the two conditions for a successful collision?

A
  1. Must have sufficient energy

2. Must collide in the correct orientation

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

Give the definition of a catalyst

A

A substance that increases the rate of reaction by providing an alternative route with lower activation energy without being used up in the process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Give the definition and an example of a homogenous catalyst

A

A homogenous catalyst is in the same phase as the reactants. E.g., concentrated sulfuric acid in formation of ester.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Give the definition and an example of heterogeneous catalysts.
Heterogeneous catalysts are in a different phase to the reactants. E.g., iron in the Haber process.
26
Give three benefits of heterogeneous catalysts
1. Easily separated from products 2. Saves energy costs 3. Benefits environment (less fossil fuel/ CO2)
27
Give four benefits of the use of enzymes as catalysts
1. Lower temp and pressure needed 2. Mild conditions - no harm to food and fabrics 3. Biodegradable - no disposal problems 4. Pure products without side reactions - no need to separate.
28
State four properties that vary with time and can therefore be used to measure rate
1. Change in gas volume (gas syringe) 2. Change in mass (weighing balance) 3. Change in colour (colorimeter) 4. Change in gas pressure (manometer)
29
Which four substances are added to the beaker so start with when studying the iodine clock reaction?
Sodium thiosulfate, starch solution, potassium iodide, sulfuric acid.
30
What is added to the beaker as a second step in the iodine clock reaction?
Hydrogen peroxide
31
In the iodine clock reaction, which substance's concentration is altered across experiments?
The hydrogen peroxide
32
Which substance makes the starch turn blue?
Iodine (not iodide!)
33
Which substance prevents the mixture turning blue immediately and why?
The sodium thiosulfate, because it turns the iodine back into iodide.
34
Give the equation of the iodide ions turning into iodine
H2O2 + 2H+ + 2I- ----> 2H2O _ I2
35
Give the equation involving thiosulfate
I2 + 2S2O3^2- ----> 2I- + S4O6 ^ 2-
36
Define hydrocarbons and functional groups
A hydrocarbon is a substance containing only hydrogen and carbon. A functional group is the group of atoms that gives the compound its characteristic properties.
37
Describe briefly these forms of writing fomulas: 1. Molecular 2. Displayed 3. Shortened 4. Skeletal
1. Molecular C6H11Br. Literally just the elements and no structural information 2. Displayed The big spidery-looking one with all the annoying hydrogens 3. Shortened Like molecular but shows structure. 4. Skeletal Even more spidery.
38
Define structural isomers
Compounds with the same formula but different structures
39
Define chain isomerism
Isomers where the C-chain changes. (what we did at GCSE. happier times.)
40
Surprise for you!
( o˘◡˘o) ┌iii┐ | Cake for you because you deserve it and you're doing so well! Keep going :)
41
Explain where E-Z isomerism can be found
In alkenes with restricted rotation about the double bond
42
Which forces do melting and boiling points depend mainly on?
Van der Walls forces
43
Which forms of bonding can be found in hydrocarbons?
Only induced dipole-induced dipole forces. Weak!
44
What effect does hydrocarbon chain length have on melting and boiling point? Why? What can you say about chain isomerism in relation to this issue?
The longer the chain, the higher the melting and boiling points. This is because VdW forces only occur on the surface, so small hydrocarbons have a smaller surface area and therefore a smaller melting point. The more branches an isomer has, the lower the boiling point and the more volatile it is :)
45
What do you need an excess of for complete combustion?
Why, O2 of course!
46
Name 2 advantages and 4 disadvantages of fossil fuels.
Advantages: 1. Large variety - can use most appropriate fuel 2. Available at all times - reliable to an extent Disadvantages: 1. Non-renewable 2. Combustion releases CO2 - fossil fuel, global warming 3. Incomplete combustion releases toxic carbon monoxide, CO 4. Produces sulfur dioxide which causes acid rain
47
What does halogenation mean
Halogenation is a reaction with any halogen
48
What is a radical
A species with an unpaired electron
49
Explain the difference between homolytic and heterolytic bond fission
Heterolytic bond fission sees the electrons both move to the same side and forming ions. Homolytic bond fission has the electrons move to opposite sides, forming free radicals.
50
How reactive are alkanes and why.
Alkanes are unreactive because they are non-polar and do not contain double bonds.
51
What do alkanes produce when combusted in oxygen?
H2O and CO2
52
Why is CO toxic?
Because it inhibits the transport of oxygen around the body
53
What needs UV light to react with alkanes?
Halogens. Halogens react with alkanes in UV light.
54
Describe briefly what happens during initiation.
UV light breaks the Cl=Cl bond homolytically to give 2Cl*
55
Give the chain propagation reaction starting with Cl*
Cl* + CH4 --> CH3* + HCl
56
Give the chain propagation reaction starting with the free radical CH3*
CH3* + Cl2 ---> CH3Cl + Cl*
57
How is a pi bond formed
By the sideways overlap of p electrons
58
What type of bonding is to be found in the double bond of alkenes?
A 3.14159265358979323846264338327950288419716939937510 bond of course! tee hee
59
What type of attack are alkenes susceptible to and why?
They are susceptible to an attack by an electrophile because of the high electron density of the pi bond
60
State the two mechanisms by which a H-Br molecule can react with a hydrocarbon
1. Heterolytic bond fission | 2. Electrophilic addition
61
Explain how a non-polar species can attack the pi bond of an alkene
Through a dipole induced by the pi bond
62
Describe two tests for the presence of a double bond
Bromine (aqueous is safer) turns from brown to colourless in the presence of an alkene Potassium manganate turns from purple to colourless in the presence of an alkene
63
What is hydrogenation of alkenes catalysed by?
Nickel
64
What is hydrogenation of alkenes used for?
To convert oils into more saturated edible fats
65
What is hydrogenation
Addition of hydrogen to an alkene
66
What type of polymerisation do alkenes undergo?
Addition polymerisation where the double bond is used and nothing is eliminated.
67
What can catalysts be used for in polymerisation?
To make straight chains which have higher density and melting temperature
68
What is hydrolysis
A reaction with water to produce a new product
69
What is a nucleophile?
A species with a lone pair of electrons which it would very much like to donate
70
Which type of attack is the carbon in a halogenoalkane susceptible to and why?
It is susceptible to nucleophilic attack because the halogen is more reactive than the carbon, creating a polar molecule where the carbon is delta positive and the halogen delta negative.
71
How can we speed up hydrolysis (OH replaces halogen)? (two ways)
Heated under reflux or addition of aqueous sodium hydroxide NaOH
72
What is a more powerful factor in reaction speed: bond strength or electronegativity?
Bond strength of course.
73
Which two functional groups are needed for a hydrocarbon to be soluble in water and why?
O-H or N-H because only they can form a hydrogen bond with water.
74
Name three uses of halogenoalkenes
1. As solvents 2. As anesthetics 3. As refrigerants
75
Describe briefly why halogenoalkanes are good solvents
They are insoluble in water (no OH or NH so no H bonding) but can mix with many other organic substances
76
Describe briefly why halogenoalkanes are good refrigerants
Because small halogenoalkanes have boiling points very close to room temperature meaning liquids can be easily evaporated and solids easily liquified. When a liquid vapourises it takes energy from the surroundings thereby cooling them.
77
State a halogenoalkane that can be used as an anesthetic
Trichloromethane (chloroform) You're doing so well! Keep going and make yourself some pancakes later!
78
What does fermentation do?
Converts sugar to ethanol
79
How is ethanol produced?
By reacting ethene with steam
80
Which substance catalyses the production of ethanol?
Phosphoric acid
81
What are the conditions for the production of ethanol?
300 degrees for high yield and rate and 60-70 atm.
82
How can alcohol by separated after fermentation?
Fractional distillation
83
Guess what
It's not in your hands
84
Define a biofuel
A biofuel is a fuel that has been produced using a biological source
85
Give three advantages of biofuels
1. Renewable (using freshly grown plants, etc) 2. Carbon neutral (release only as much as they have taken out 3. Better economic and political stability (no need to import/rely on other countries for fossil fuels if you don't have any)
86
Give three disadvantages of biofuels
1. Woodland often cut down to produce land - land also cannot produce food crops 2. Large quantities of water and fertilizer needed - causes water shortages and pollution 3. Energy needed to transport the resulting fuel and build factories so not really carbon neutral after all
87
What does an alcohol form when dehydrated?
An alkene
88
Draw the dehydration of propanol
. . l . . l . . l . . . . . . . . . . . . . l . . l . . .l - C - C - C - O - H -----> - C - C = C + H - O - H . . l. . . l. . .l. . . . . . . . . . . . . l. . .l. . . .l I tried my best with the diagram. Ignore the dots.
89
How many other carbons is the C-OH carbon joined to in a primary alcohol?
Less than or equal to one
90
How many other carbons is the C-OH carbon joined to in a secondary alcohol?
Two
91
How many other carbons is the C-OH carbon joined to in a tertiary alcohol
Three
92
Name the product(s) of a primary alcohol's oxidation(s)
1. (propan)al - aldehyde | 2. (propan)oic acid - carboxylic acid
93
Name the product(s) of a secondary alcohol's oxidation(s)
(propan)one - ketone
94
Name the product(s) of a tertiary alcohol's oxidation(s)
(2-methylpropan-2-)ol - just an alcohol because tertiary alcohols don't get oxidised!
95
What is the reaction that takes place when testing for a primary or secondary alcohol, which reagents are used, and what is the observation?
Oxidation, acidified potassium dichromate, orange to green
96
Give the definition of a weak acid
One that only partially ionises in an aqueous solution
97
Are carboxylic acids strong or weak?
Weak! | Unlike you, my dear :)
98
Acid + Base -->
Salt + water
99
Acid + carbonate --->
Salt + carbon dioxide + water
100
Acid + alcohol --->
Ester + water (that one's nasty)
101
Describe the smell of esters
Sweet and fruity :)
102
Guess what.
You are doing so well. God is with you.

Chemistry (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions