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Chemistry > C6 Electrolysis Papers Part 2 > Flashcards

C6 Electrolysis Papers Part 2 Flashcards

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1
Q

What is the Reaction to produce iron from iron oxide

A

Carbothermal reduction

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2
Q

Why electrically conductive aluminium is used to make cans

A

Low density

Less resistance to corrosion

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3
Q

Why the positive electrode must be continually replaced

A

Electrode reacts with oxygen

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4
Q

Calculate the mass of oxygen produced when 2000 kg of aluminium oxide is completely electrolysed

A

2 Mr of Al2O3 = 204

204 (kg of Al2O3) gives 96 kg of O2

(2000 ➗ 204) x 96 = 941kg

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5
Q

Why sodium chloride solution can’t be used as the electrolyte to produce sodium metal

A

Hydrogen would be produced instead of sodium as sodium is more reactive than hydrogen

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6
Q

Calculate the volume of 150 kg of chlorine gas at room temperature and pressure

The volume of one mole of any gas at room temperature and pressure is 24.0 dm3

Relative formula mass (M.): Cl = 71

A

150,000
_________ x 24 = 50,704dm3 so 50,700dm3

 71
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7
Q

Which line in figure 3 shows volume of gas collected is directly proportional to time

A

Hydrogen line only

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8
Q

Why can graphite conduct electricity

A

Has delocalised electrons

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9
Q

What is produced at cathode/anode molten zinc chloride

A

Cathode - zinc as zinc is more reactive than hydrogen

Anode - chlorine as it is halide so chlorine is produced not oxygen

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10
Q

What is produced at cathode/anode potassium bromide

A

Cathode - hydrogen as potassium is more reactive than hydrogen

Anode - bromine as it is halide

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11
Q

Why wouldn’t electrolysis work if was solid sodium chloride

A

Solid zinc chloride does not conduct electricity as ions cannot move in solid

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12
Q

How graphite conducts electricity answer in terms of structure and bonding in graphite

A

Each carbon atoms forms 3 covalent bonds

1 electron per carbon atom is delocalised

So these electrons carry charge through the graphite

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13
Q

The student made an error in selecting the apparatus for this investigation

How should the apparatus be changed

Give one reason for your answer

A

Use measuring cylinders instead of test tubes as test tubes can’t measure volume

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14
Q

Describe trends in results above of hydrogen and chlorine increasing graph

A

Volume of hydrogen collected is directly proportional to time

Rate of collection of hydrogen is 0.45 cm/min

Up to 8 minutes chlorine is collected at increasing rate

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15
Q

No gas escapes from the apparatus

Suggest one reason for the difference in volume of each gas collected

A

Chlorine reacts with water

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16
Q

Calculate the amount in moles of chlorine collected after 20 minutes

Use Figure 3

The volume of one mole of any gas at room temperature and pressure is 24.0 dm

A

6.6 ➗ 1000 = 0.0066

0.0066 ➗ 24 = 2.75 x 10^ -4

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17
Q

Independant variable

A

The variable that changes during an experiment

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18
Q

Dependant variable

A

Variable being tested or measured

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19
Q

Control variable

A

Variable that is kept the same during scientific experiment

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20
Q

Independant variable for electrolysing salt solutions with inert electrodes

A

Salt solutions

21
Q

Observation for electrolysing salt solutions with inert electrodes

A

Solid/metal deposit on negative electrode

22
Q

Why the product at negative electrode is not always a metal

A

Hydrogen produced when metal is more reactive than hydrogen

23
Q

Why does iodine have higher boiling point than chlorine

A

Forces between iodine atoms are stronger

24
Q

Predict the boiling point of bromine

A

Anything in range +30 to +120

25
Q

Trend in boiling point group 1 and halogens

A

Group 1 - decreases as goes down group

Halogens - increases as goes down group

26
Q

Why trend in reactivity decreases halogens as go down group

A

Atomic mass of the halogens increases

Increase in electron shells

Atoms get larger as go down group

Attraction to outer electron from nucleus decreases

27
Q

Why trend in reactivity increases group 1 as go down group

A

Atoms become larger

Outer electron becomes further from the nucleus

Attraction between nucleus and outer electron gets weaker so electron is more easily lost

28
Q

Why trend in boiling point increase down group 7

A

Atoms increase in size as they gain extra electron shells

Intermolecular forces become stronger

More energy is required to break these forces

29
Q

Why trend in boiling point decrease down group 1

A

Additional shell being added to the previous element causes atomic radius to increase

The increasing atomic radius means weaker forces between atoms so lower melting and boiling point

30
Q

What colour is final solution of reaction chlorine added to potassium iodide solution

A

Brown

31
Q

REACTIVITY SERIES

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
CARBON
Zinc
Iron
Tin
Lead
HYDROGEN
Copper
Silver
Gold
Platinum

32
Q

Ionic equation for reaction of chlorine with potassium iodide

A

2I- + Cl2 ———> I2 + 2Cl-

33
Q

Why is potassium not included in

Ionic equation for reaction of chlorine with potassium iodide

A

It is a spectator ion and dissociates in aqueous solution

Potassium ions do not undergo any chemical change during reaction and don’t affect redox process therefore excluded from net ionic equation

34
Q

Spectator ion

A

Ions that are present in the reaction mixture but don’t participate in the chemical reaction

They remain unchanged throughout the process

35
Q

Why potassium iodide conducts electricity

A

Contains ions which can move

36
Q

Transition metals ions

A

+2

37
Q

Which electrode does oxidation happen in

A

Positive anode

38
Q

Which electrode does reduction happen in

A

Negative cathode

39
Q

Why zinc ions move towards negative electrode

A

Zinc ions are positive and opposite charges attract

40
Q

What type of reaction occurs when the zinc ions gain electrons

A

Reduction

41
Q

Why alloy is harder than pure zinc

A

Different sized atoms

No layers or rows so can’t slide

42
Q

Alloys can be bent. Some alloys return to their original shape when heated

What name is used for these alloys

A

Shape memory

43
Q

What happens when a magnesium atom reacts with chlorine atoms to produce magnesium chloride.

A

Magnesium loses 2 electrons and chlorine gains 1 electron

Forms ionic bonds

Electrostatic attraction between ions

8 electrons in outer shell

44
Q

Why magnsium chloride must be molten or dissolved in water to be electrolysed

A

Ions can move to electrodes and carry charge

45
Q

How magnsium is produced at negative electrode

A

Magnesium ions attracted to electrode so magnsium ion gains 2 electrons

46
Q

Why magnesium is not produced at negative electrode

A

Magnesium is more reactive than hydrogen

47
Q

Complete and balance the half equation for the reaction at the positive electrode.

_______ Cl- ———-> Cl2 + _________

A

2Cl- ——-> Cl2 + 2e-

48
Q

Why metals can be bent and shaped

A

Layers of particles can slide

Chemistry (10 decks)

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