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Most Difficult Topics Flashcards

1
Q

Which ions do anodes attract?

A

Anions

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2
Q

Which ions do cathodes attract?

A

Cations

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3
Q

What is the electrolyte in electrolysis

A

The substance that the electrolysis is done on

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4
Q

Define the term reduction

A

When a substance gains electrons

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5
Q

Define the term oxidation

A

When a substance loses electrons

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6
Q

Which reaction happens at the anode?

A

Oxidation

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7
Q

Which reaction happens at the cathode?

A

Reduction

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8
Q

What is the overall reaction for the extraction of iron?

A

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

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9
Q

What happens when C reacts with O2

A

It increases the temperature to 2000C and forms CO2

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10
Q

CO2 + C ->

A

2CO

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11
Q

3CO + Fe2O3 ->

A

2Fe + 3CO2

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12
Q

What is the main impurity of hematite

A

SiO2 (sand)

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13
Q

Which chemical is used to remove SiO2 from iron?

A

CaCO3 (limestone)

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14
Q

What is the first step?

A

CaCO3 -> CaO + CO2

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15
Q

CaO + SiO2 ->

A

CaSiO3

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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.

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17
Q

What is CaSiO3 used for?

A

Road surfacing

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18
Q

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

A

It is more reactive than carbon

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19
Q

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

A

Graphite

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20
Q

What is produced at the anode in electrolysis of Aluminium?

A

Oxygen

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21
Q

What is produced at the cathode in electrolysis of Aluminium?

A

Aluminium

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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.

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23
Q

What is one use of aluminium?

A

Making Planes

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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.

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25
Q

Extraction of Aluminium is bad for the environment. What is used to lower the energy demand?

A

Cryolite (Na3AlF6)
(Sodium, Aluminium, Flouride)

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26
Q

How does Cryolite reduce the energy demand?

A

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
Q

What is the reactivity series for metals (and also C and H)?

A

K, Na, Li, Ca, Al, C, Zn, Fe, H, Cu, Ag, Au

28
Q

How are the elements less reactive than C extracted?

A

Carbon reduction

29
Q

Which ions react with dilute acids?

A

The ones that are more reactive than H

30
Q

If there are 2 cations in a solution, which one reacts with the cathode?

A

The less reactive one (going from ion to metal has a reverse reactivity series)

31
Q

If there are 2 anions in a solution, which one reacts with the anode?

A

The less reactive one

32
Q

What is the full reactivity series of anions for losing electrons (going back to metal state)?

A

Least likely to: CO3(2-), NO3-, SO4(2-)
OH-
Cl-
Br-
Most likely to: I-

33
Q

Example: If NaCl (aq) is electrolysed, what is formed at the anode and cathode?

A

H2 at the cathode
Cl2 at the anode

34
Q

If NaCl (aq) is electrolysed, what is the remaining solution

A

NaOH (base)

35
Q

What happens if OH- is oxidised at an anode?

A

2OH- - 4e- -> O2 + 2H+ (possible to figure this out, but easier to remember)

36
Q

(Solubility Rules)
Group 1 compounds are always ______

37
Q

Nitrate compounds are always ______

38
Q

Chloride compounds are _______ except for ________

A

soluble, except with Pb2+ and Ag+

39
Q

Sulfate compounds are _________ except for _______

A

soluble, except with Ba2+, Ca2+, Pb2+

40
Q

Carbonate compounds are ________
except for ________

A

insoluble, except with group 1 ions

41
Q

Hydroxide compounds are ________
except for ________

A

insoluble, except with gp1, Calcium, and ammonium ions

42
Q

How does Temperature affect position of equilibrium and why?

A

-Increases both rates of reaction
-Endothermic needs more Ea
-Endothermic is increased more
-Position shifts towards endothermic reaction

43
Q

Pressure only affects the rate of reactions involving _____

44
Q

How and why does pressure affect the position of equilibirium?

A

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
Q

Catalysts do not change the position of equilibrium. Why are they used in reversible reactions?

A

They decrease the time it takes to reach equilibrium by speeding up both reactions equally

46
Q

What is the first step of the contact process?

A

S + O2 -> SO2

47
Q

What is the second step of the contact process?

A

2SO2 + O2 <=> 2SO3

48
Q

Is the forward reaction for the second step of the Contact Process exothermic or endothermic?

A

Exothermic

49
Q

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)

A

SO3 + H2O -> H2SO4

50
Q

What are the optimum conditions for the Contact Process?

A

Temperature: Low
Pressure: High
Catalyst: Powdered V2O5 (powder used for increased surface area of catalyst)

51
Q

What is the actual temperature used in the Contact Process?

A

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
Q

What is the actual pressure used in the Contact Process?

A

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
Q

Why is the theoretical overall reaction (SO3 + H2O) not actually done?

A

It is highly exothermic and therefore dangerous.

54
Q

Which 2 reactions are done instead?

A

SO3 + H2SO4 -> H2S2O7 (oleum)
H2S2O7 + H2O -> 2H2SO4

55
Q

What is the use of ammonia?

A

When reacted with an acid it forms a salt, that can be used as an explosive or a fertiliser

56
Q

What is the overall reaction for the Haber Process?

A

N2 + 3H2 <=> 2NH3

57
Q

Which reactions are used to make fertiliser?

A

NH3 + HCl -> NH4Cl
NH3 + HNO3 -> NH4NO3 (better fertiliser)

58
Q

Which reaction is used to make an explosive?

A

NH3 + HNO3 -> NH4NO3

59
Q

What is the optimum temperature for the haber process?

60
Q

What is the optimum pressure for the haber process?

61
Q

Which catalyst is used in the Haber Process?

A

Powdered Iron (surface area)

62
Q

What is the actual pressure used in the Haber Process?

A

200Atm (somewhat high)
*If over 400Atm is used, it would be better but very expensive

63
Q

What is the actual temperature used in the Haber Process?

A

450C (medium) to ensure a decent rate and yield.
Because:
Too high -> Low Yield
Too low -> Low Rate

64
Q

How is ammonia extracted at the end of the Haber Process?

A

Everything is cooled (N2, H2, NH3), and NH3 condenses as it has a higher boiling point than N2 and H2.

IGCSE Chemistry (23 decks)

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