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GCSE Chemistry > Unit 2: 5.4 - Electrolysis > Flashcards

Unit 2: 5.4 - Electrolysis Flashcards

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1
Q

What is electrolysis?

A

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

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2
Q

What is the name of the substance which is broken down?

A

The electrolyte

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3
Q

What type of substance are the electrodes made of? Give an example.

A

An inert subtance. E.g. Carbon

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4
Q

Negatively charged ions move towards which electrode?

A

The anode, (+)

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5
Q

Positively charged ions move to which electrode?

A

The cathode, (-)

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6
Q

Positively charged ions form which atoms during electrolysis?

A

Metal or hydrogen, depending on which ions are present.

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7
Q

Negatively charged ions form which atoms during electrolysis?

A

Non-metallic

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8
Q

What state must the ionic compound be in during electrolysis and why?

A

Liquid (l) or in an aqueous solution (aq) so the electrons are able to freely move around and conduct electricity.

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9
Q

State the processes undergone by molten lead bromide during electrolysis.

A

The lead attracts to the anode, where is gains an electron. The bromide goes to the cathode, where it loses an electron, and becomes bromine gas.

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10
Q

What is reduction?

A

Reduction Is Gain (of electrons) (OILRIG)

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11
Q

What is oxidisation?

A

Oxidisation Is Loss (of electrons) (OILRIG)

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12
Q

Complete the half equation for chlorine:

2Cl- –> ….+….

A

2Cl- –> 2e- + 2Cl

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13
Q

Under what circumstances is hydrogen formed at the cathode?

A

When solutions of ions water are electrolysed and if the other positive ions in the solution are those of a metal MORE reactive than hydrogen.

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14
Q

What is usually produced at the anode from aqueous solutions?

A

Oxygen

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15
Q

When is a halogen sometimes produced at the anode?

A

If the solution contains a reasonably high concentration of halide ions.

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16
Q

Why must aluminium be extracted using electrolysis?

A

It is more reactive than carbon.

17
Q

What ionic compound is aluminium oxide added to during electrolysis?

A

Cyrolite.

18
Q

What is the normal melting point for aluminium and why is this not good?

A

2000 degrees Celsius. This is bad as it would require lots of energy.

19
Q

What temperature is aluminium oxide electrolysed at?

A

850 degrees Celsius.

20
Q

Give the symbol and word equation for the electrolysis of aluminium oxide.

A

2Al2O3(l) –>4Al (l) + 3O2 (g)

Aluminium oxide –> Aluminium + Oxygen

21
Q

Give the half equations of almunium oxide at the negative and positive electrode.

A

-: Al3+ (l) + 3e- –> Al (l)

+: 2O2- (l) –> 2O2 (g) + 4e-

22
Q

How do the high temperatures effect the carbon electrodes?

A

The oxygen bonds with the carbon producing CO2, meaning they have to be replaced regularly.

23
Q

Which ions does brine contain?

A

Na+, Cl-, H+, OH- (all aq)

24
Q

What is released from brine at each electrode?

A

Anode: Chlorine. Cathode: Hydrogen

25
Q

What is left after the electrolysis of brine?

A

A solution of sodium ions and hydroxide ions, NaOH (aq), sodium hydroxide

26
Q

What are the products of the electrolysis of brine used for?

A

Hydrogen: Hardening oils (e.g. making margarine) and Hydrochloric acid.
Chlorine: Used as a disinfectant and bleach, as well as used to make plastics.
Sodium hydroxide: Soap, Paper, Neutralising acids (as it’s a strong alkali).

27
Q

Give 4 uses of electroplating

A
  • To make an object more attractive
  • Corrosion protection
  • Increasing the hardness of an object
  • Reduce costs by just using a thin layer.
28
Q

The object to be electroplated is used as which electrode?

A

The negative, as the positive metal ions will be attracted to it.

29
Q

How is the metal plated onto the other metal?

A

The ions in the solution are attracted to the negative electrode. These become neutral atoms and are held on by metallic bonding.

30
Q

The object which is to be used as a plating metal is used as which electrode?

A

The positive

31
Q

What does the electrolyte need to contain in electroplating?

A

Ions of the plating metal.

32
Q

Describe the process during electroplating

A
  • At the anode, atoms of the plating metal lose electrons to form metal ions which enter the solution.
  • At the cathode, +ive metal ions gain electrons which plate onto the cathode.

GCSE Chemistry (16 decks)

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