Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

IGCSE Chemistry > Most Difficult Topics > Flashcards

Most Difficult Topics Flashcards

1
Q

Which ions do anodes attract?

A

Anions

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

Which ions do cathodes attract?

A

Cations

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

What is the electrolyte in electrolysis

A

The substance that the electrolysis is done on

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

Define the term reduction

A

When a substance gains electrons

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

Define the term oxidation

A

When a substance loses electrons

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

Which reaction happens at the anode?

A

Oxidation

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

Which reaction happens at the cathode?

A

Reduction

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

What is the overall reaction for the extraction of iron?

A

2Fe2O3 + 3C -> 3CO2 + 4Fe

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

What happens when C reacts with O2

A

It increases the temperature to 2000C and forms CO2

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

CO2 + C ->

A

2CO

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

3CO + Fe2O3 ->

A

2Fe + 3CO2

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

What is the main impurity of hematite

A

SiO2 (sand)

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

Which chemical is used to remove SiO2 from iron?

A

CaCO3 (limestone)

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

What is the first step to remove sand?

A

CaCO3 -> CaO + CO2

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

CaO + SiO2 ->

A

CaSiO3

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

How is CaSiO3 removed from iron?

A

The molten iron sinks to the bottom due to being more dense than CaSiO3, so the Fe can be removed with a tap.

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

What is CaSiO3 used for?

A

Road surfacing

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

Why can Al not be extracted by carbon reduction (displacement)?

A

It is more reactive than carbon

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

Which material are the electrodes made of in the electrolysis of Aluminium

A

Graphite

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

What is produced at the anode in electrolysis of Aluminium?

A

Oxygen

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

What is produced at the cathode in electrolysis of Aluminium?

A

Aluminium

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

Why do anodes need to be replaced over time?

A

At the hot temperature required to melt Al, oxygen reacts with graphite, making CO2, and eroding the anode.

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

What is one use of aluminium?

A

Making Planes

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

What do the electrodes look like in the industrial electrolysis of aluminium?

A

Anodes are attached to the same cell, many of them at the same time. The cathode is the chamber itself.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Extraction of Aluminium is bad for the environment. What is used to lower the energy demand?
Cryolite (Na3AlF6) (Sodium, Aluminium, Flouride)
26
How does Cryolite reduce the energy demand?
It has ions with lower magnitude of charge, that decrease the melting point of the electrolyte when mixed into it. (It also doesn't react with electrodes btw)
27
What is the reactivity series for metals (and also C and H)?
K, Na, Li, Ca, Al, C, Zn, Fe, H, Cu, Ag, Au
28
How are the elements less reactive than C extracted?
Carbon reduction
29
Which ions react with dilute acids?
The ones that are more reactive than H
30
If there are 2 cations in a solution, which one reacts with the cathode?
The less reactive one (going from ion to metal has a reverse reactivity series)
31
If there are 2 anions in a solution, which one reacts with the anode?
The less reactive one
32
What is the full reactivity series of anions for losing electrons (going back to metal state)?
Least likely to: CO3(2-), NO3-, SO4(2-) OH- Cl- Br- Most likely to: I- Always OH- unless the halide is concentrated
33
Example: If NaCl (aq) is electrolysed, what is formed at the anode and cathode?
H2 at the cathode Cl2 at the anode
34
If NaCl (aq) is electrolysed, what is the remaining solution
NaOH (base)
35
What happens if OH- is oxidised at an anode?
4OH- -> O2 + 2H2O + 4e- (easier to memorise than figure out each time)
36
(Solubility Rules) Group 1 compounds are always ______
Soluble
37
Nitrate compounds are always ______
Soluble
38
Chloride compounds are _______ except for ________
soluble, except with Pb2+ and Ag+
39
Sulfate compounds are _________ except for _______
soluble, except with Ba2+, Ca2+, Pb2+
40
Carbonate compounds are ________ except for ________
insoluble, except with group 1 ions
41
Hydroxide compounds are ________ except for ________
insoluble, except with gp1, Calcium, and ammonium ions
42
How does Temperature affect position of equilibrium and why?
-Increases both rates of reaction -Endothermic needs more Ea -Endothermic is increased more -Position shifts towards endothermic reaction
43
Pressure only affects the rate of reactions involving _____
gases
44
How and why does pressure affect the position of equilibirium?
Position shifts to the side with fewer moles of gas, as the side with more moles of gas will see a greater increase in reaction rate.
45
Catalysts do not change the position of equilibrium. Why are they used in reversible reactions?
They decrease the time it takes to reach equilibrium by speeding up both reactions equally
46
What is the first step of the contact process?
S + O2 -> SO2
47
What is the second step of the contact process?
2SO2 + O2 <=> 2SO3
48
Is the forward reaction for the second step of the Contact Process exothermic or endothermic?
Exothermic
49
What is the overall reaction for the last 3 steps of the Contact Process (this reaction does not actually happen, but is considered for equilibrium questions)
SO3 + H2O -> H2SO4
50
What are the optimum conditions for the Contact Process?
Temperature: Low Pressure: High Catalyst: Powdered V2O5 (powder used for increased surface area of catalyst)
51
What is the actual temperature used in the Contact Process?
400 Celsius is used High Temp would produce low yield with a fast rate Low Temp would produce high yield with a slow rate Medium temperature is used to get the benefits of both
52
What is the actual pressure used in the Contact Process?
1-2Atm (Low) Contact Process yield, even at a low pressure is over 99%, so it is not worth it to use a higher pressure (more expensive)
53
Why is the theoretical overall reaction (SO3 + H2O) not actually done?
It is highly exothermic and therefore dangerous.
54
Which 2 reactions are done instead of SO3 + H2O?
SO3 + H2SO4 -> H2S2O7 (oleum) H2S2O7 + H2O -> 2H2SO4
55
What is the use of ammonia?
When reacted with an acid it forms a salt, that can be used as an explosive or a fertiliser
56
What is the overall reaction for the Haber Process?
N2 + 3H2 <=> 2NH3
57
Which reactions are used to make fertiliser?
NH3 + HCl -> NH4Cl NH3 + HNO3 -> NH4NO3 (better fertiliser)
58
Which reaction is used to make an explosive?
NH3 + HNO3 -> NH4NO3
59
What is the optimum temperature for the haber process?
Low
60
What is the optimum pressure for the haber process?
High
61
Which catalyst is used in the Haber Process?
Powdered Iron (surface area)
62
What is the actual pressure used in the Haber Process?
200Atm (somewhat high) *If over 400Atm is used, it would be better but very expensive
63
What is the actual temperature used in the Haber Process?
450C (medium) to ensure a decent rate and yield. Because: Too high -> Low Yield Too low -> Low Rate
64
How is ammonia extracted at the end of the Haber Process?
Everything is cooled (N2, H2, NH3), and NH3 condenses as it has a higher boiling point than N2 and H2.

IGCSE Chemistry (23 decks)

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