Electrolysis Flashcards

0
Q

Why do solid ionic compounds do not conduct electricity but molten or dissolved ionic compounds do?

A

Ions cannot move in solid.

Ions can move when molten or dissolved.

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1
Q

What is an electrolyte?

A

A molten or dissolved ionic compound that decomposes when it conducts electricity.

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2
Q

Define oxidation and reduction

A

OIL RIG
Oxidation is the loss of electrons
Reduction is the gain of electrons

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3
Q

What is formed at the anode and cathode when a molten ionic compound conducts electricity?

A

Anode- non metal forms

Cathode- metal forms

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4
Q

What are the possible products at the anode and cathode when a solution conducts electricity?

A

Anode- halogen or oxygen ( from the water )

Cathode- metal or hydrogen (from the water)

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5
Q

Which ions are attracted to the positive electrode(anode)?

A

Negative ions

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6
Q

Which ions are attracted to the negative electrode(cathode)?

A

Positive ions

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7
Q

What is brine?

A

Concentrated sodium chloride solution.

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8
Q

What is formed at the cathode when brine undergoes electrolysis?

A

Hydrogen

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9
Q

What is formed at the anode when brine undergoes electrolysis?

A

Chlorine

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10
Q

What is left in solution when brine undergoes electrolysis?

A

Sodium hydroxide solution

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11
Q

Give a use of chlorine

A

Killing bacteria in drinking water, swimming pools , or making bleach

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12
Q

Give a use or hydrogen

A

Making margarine or as a rocket fuel

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13
Q

Give a use of sodium hydroxide

A

Making bleach and soap

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14
Q

Which 4 ions are in sodium chloride solution?

A

Na+
OH-
H+
Cl-

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15
Q

Electrolysis of brine: give the half equation at the anode

A

2Cl- –> Cl2 + 2e

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16
Q

Electrolysis of brine: give the half equation at the cathode

A

2H+ + 2e- –> H2

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17
Q

What is bauxite and what compound does it mainly contain?

A

An ore that contains aluminium oxide

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18
Q

Extraction of aluminium: why is cryolite used?

A

To lower the melting point so less energy is needed

19
Q

Extraction of aluminium: why do the anodes have to be replaced regularly?

A

The oxygen produced reacts with carbon anodes to produce carbon dioxide so they burn away.

20
Q

Extraction of aluminium : what is missing from this half equation?
Al3+ + _____ –> Al

A

3e-

21
Q

Extraction of aluminium: what is missing from this half equation?
2O2- -> O2 + ______

A

4e-

22
Q

Extraction of aluminium: what is produced at the anode and cathode?

A

Anode- oxygen

Cathode- aluminium

23
Q

Electrolysis of MOLTEN SODIUM CHLORIDE: what is produced at the anode and cathode?

A

Anode- chlorine

Cathode- sodium

24
Q

Electrolysis of copper chloride solution: what is produced at the anode and cathode?

A

Anode- chlorine

Cathode- copper

25
Q

Electrolysis of copper sulphate solution: what is produced at anode and the cathode?

A

Anode- oxygen

Cathode- copper

26
Q

Which substance produces zinc at the cathode and chlorine at the anode?

A

Molten zinc chloride

27
Q

Define electrolysis

A

The process that uses electricity to break down ionic compounds into elements.

28
Q

The substance that breaks down is called the…?

A

Electrolyte

29
Q

What must be done to ionic compounds before they can be electrolysed?

A

It must be dissolved or melted

30
Q

What are the electrodes made from?

A

An inert substance that does not react with the products

31
Q

Fill in the gap:

The ions in the electrolyte move to the electrodes where they are discharged to produce ________

A

Elements

32
Q

Fill in the gaps:

Positively charged _______ are attracted to the _________ electrode where they form ________ or _________.

A

Ions
Negative
Metals or hydrogen

33
Q

Fill in the gaps:
Negatively charged ________ are attracted to the _________ electrode where they lose their charge to form non- metallic elements.

A

Ions

Positive

34
Q

An ion always moves to the ?

A

Oppositely charged electrode

35
Q

Fill in the gaps:
When positively charged ions reach the ________ electrode they ________ electrons to become neutral atoms.
This is called?

A

Negative
Gain
Reduction

36
Q

At the positive electrode, negative ions ______ electrons to become neutral atoms.
This is called?

A

Lose

Oxidation

37
Q

What’s the half equation at the anode for lead bromide?

A

2Br–> Br2 + 2e-

38
Q

What’s the half equation at the cathode for lead bromide?

A

Pb2+ + 2e- –> Pb

39
Q

How is aluminium manufactured?

A

Aluminium oxide is electrolysed

40
Q

What forms at the cathode and anode during the extraction of Aluminium?

A

Anode- oxygen

Cathode - aluminium

41
Q

What products do we get when we electrolyse brine?

A

Chlorine gas, hydrogen gas, sodium hydroxide solution

42
Q

Why is hydrogen produced when sodium chloride is electrolysed?

A

The solution contains hydrogen ions which are discharged in preference to sodium ions because sodium is more reactive than hydrogen.

43
Q

Why is the electrolysis of brine an important industrial process?

A

It’s three products have many uses

44
Q

Why can we electroplated objects?

A

To improve their appearance , protect their surface, and use smaller amounts of precious metals.

45
Q

Why,are some knives, forks and spoons silver plated?

A

To make them look attractive, to protect the metal from corrosion and to reduce costs.