Topic 5 - Electrolysis (Year 10) Flashcards

1
Q

What is the name given to the negative electrode in elecotrolysis?

A

Cathode

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2
Q

What is the name given to the positive electrode in elecotrolysis?

A

Anode

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3
Q

What is an electrolyte?

A

Solution of ions that can conduct electricity

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4
Q

What term can be used to remember which elctrode has which charge?

A

PANIC (Positive Anode Negative Is Cathode)

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5
Q

Which Electrode would a Pb2+ ion move towards in the electrolysis of molton lead bromide?

A

Negative

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6
Q

What type of electrodes are used in electrolysis?

A

Two inert, carbon electrodes

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7
Q

Define electrolysis

A

The spliiting up of an ionic compound into it’s constituent elements usinng electricity

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8
Q

What would be produced at the negative electrode in the electrolysis od NaCl?

A

Na (Sodium)

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9
Q

What would be produced at the positive electrode in the electrolysis od NaCl?

A

Cl2 (Chlorine)

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10
Q

Describe how the electrolysis of a molten ionic substance is carried out in a lab

A

Two inert electrodes are cleaned using sand paper. The ionic compound is heated in a crucible over a bunsen burner. The electrodes are placed into the electrolyte and connected to a power source.

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11
Q

Give the half equation for the reduction of K+ ions during the electrolysis of KCl

A

K+ + e- → K

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12
Q

Give the half equation for the oxidation of Cl- ions during the electrolysis of KCl

A

2Cl- → Cl2 + 2e-

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13
Q

Give the name of the ions produced when water molecules are broken down

A

H+ and OH- (Hydrogen ion and Hydroxide Ion)

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14
Q

Can ionic substances be electrolysed when solid?

A

No

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15
Q

Why can’t ionic substances be electrolysed when solid?

A

ions cannot move.

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16
Q

What will be produced at the positive electrode in a solution containing both OH- ions and Cl- ions?

A

Chlorine (Cl2)

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17
Q

What will be produced at the positive electrode in a solution containing both OH- ions and SO42- ions?

A

Oxygen (O2)

18
Q

Why in a solution where sodium chloride has been dissolved in water. In electrolysis sodium isn’t produced at the negative electrode?

A

Sodium is more reactive than hydrogen, therefore it stays in the solution and Hydrogen would be formed

19
Q

What is the half equation for the reduction of hydrogen ions?

A

2H+ + 2e- → H2

20
Q

What are the four different ions present in a copper sulfate solution?

A

Cu2+, H+, SO42-, OH-

21
Q

What are the products formed at the anode and cathode in the electrolysis of sopper sulfate solution?

A

Oxygen is produced at the anode, Copper is produced at the cathode

22
Q

Explain how the electrolysis of copper sulfate can be used to purify copper

A

An impure sample of copper is used as the anode and a thin pure piece of copper is used as the cathode. The impure copper is oxidised and dissolved into the solution of ions. The copper ions in the solution are reduced at the cathode, forming a layer of pure copper of the electrode.

23
Q

What are the two half equations for the electrolysis of copper sulfate solution using copper electrodes?

A

Cu2+ + 2e- → Cu and Cu → Cu2+ + 2e-

24
Q

What ions would NaCl split into when molten?

A

Na+ + Cl-

25
Q

What ions would CuSO4 split into when molten?

A

Cu2+ + SO42-

26
Q

Descirbe what you would expect to see when conducting the electrolysis of copper chloride solution using graphite (inert) electrodes.

A

The cathode will be coated with a brownish layer.

This shows copper is being produced

At the anode there will be bubbles.

This indicates that a gas is being produced

If you hold a damp blue litmus paper near this, it will turn red and then bleach white.

This indicates that the gas produced is chlorine

27
Q

Descirbe what you would expect to see when conducting the electrolysis of copper chloride solution using an impure copper anode and a pure copper cathode.

A

The anode will appear to be smaller (it will have lost mass)

The cathode will appear bigger (it has gained mass)

Under the anode, there will be a collection of impurities that have settled

This shows that the pure copper ions have migrated from the anode to the cathode

28
Q

What’s attracted to cathodes and what charge?

A

Cations (positive)

29
Q

What’s attracted to anodes and what charge

A

Anions (negative)

30
Q

What happens when the cations reach the cathode?

A

They are reduced (gain electrons) and discharged.

31
Q

When anions move to the anode, what do they do?

A

They are oxidised (lose electrons) and so are discharged

32
Q

What happens at the cathode in electrolysis of aqueous solutions?

A

If the metal is more reactive than hydrogen, hydrogen is produced. If the metal is less reactive than hydrogen, the metal is produced.

33
Q

What happens at the anode in electrolysis of aqueous solutions?

A

If a halide is present, the halide is produced. If there’s no halide present, oxygen is produced.

34
Q

In purification if copper what’s the cathode made out of?

A

Pure copper

35
Q

In purification of copper, what’s the anode made out of?

A

Impure copper

36
Q

In purification of copper, what’s the electrolyte?

A

In purification of copper, what’s the electrolyte ?

37
Q

In purification of copper, what is the colopur of copper sulphate?

A

Blue

38
Q

What’s the voltage directly proportionate to in purification of copper?

A

The mass of the cathode due to quicker donation and loss of electrons.

39
Q

What does the cathode do in purification of copper ?

A

It grows heavier due to reduction of copper ions leading to discharged atoms deposited on the cathode.

40
Q

What does the anode do during copper purification?

A

It grows lighter due to oxidisation of the impure copper molecules causing more copper to dissolve into the solution. The impurities are left as a slush at the bottom.

41
Q
A