Electrolysis

Question 1

What is an electric current

Answer 1

A flow of electrons or ions

Question 2

Why do covalent compounds not conduct electricity

Answer 2

They don’t have charged particles so they consist of atoms or molecules therefore they can’t conduct electricity, even if they melt or dissolve in water.

Question 3

Why do ionic compounds conduct electricity only when molten or in solution

Answer 3

Ionic compounds have charged particles but can only conduct if it is molten or dissolved in water because only in the liquid or aqueous state can the ions move to the oppositely charged electrode.

Question 4

Sodium chloride electrolysis

Answer 4

Diaphragm cell
Hydrogen gas at cathode
Chlorine gas at anode
Sodium hydroxide in solution

2H + + e- ——> H2
2Cl- ——> Cl2 + e-

Uses:

• chlorine sterilises water
• hydrogen for Haber process and to change oils and fat into margarine
• sodium hydroxide chemical industry for soap and bleach

Question 5

Copper sulfate electrolysis

Answer 5

Copper : cathode (Cu2+ + 2e- ——> Cu)

Hydroxide : anode (

Question 6

Electrolyte definition

Answer 6

Liquid that conducts electricity

Question 7

Electrolysis definition

Answer 7

Separation of an ionic compound using electricity

Question 8

Cation/cathode

Answer 8

Positively charged ion/ negatively charged electrode

Question 9

Anion/ anode

Answer 9

Negatively charged ion/ positively charged electrode

Question 10

Electrode definition

Answer 10

Terminals of battery dipping into an electrolyte

Question 11

Inert definition

Answer 11

Unreactive atom

Question 12

Definition of reduction and oxidation

Answer 12

Reduction : gaining electrons, occurs at the cathode

Oxidation : losing electrons, occurs at the anode

Question 13

Lead bromide products

Answer 13

Lead, bromine

Question 14

What does electrolysis involve

Answer 14

It involves the formation of new substances when ionic compounds conduct electricity

Question 15

Sulfuric acid products

Answer 15

4 hydrogens, 1 oxygen

Question 16

Sodium chloride products (L)

Answer 16

2 sodiums, 1 chlorine

Question 17

Sodium chloride products (aq) diaphragm cell

Answer 17

Hydrogen, chlorine

• titanium anode
• mild steel cathode

Question 18

Copper sulfate (aq)

Answer 18

2 coppers, 1 oxygen

Question 19

Rules of electrolysis: cathode

Answer 19

Metal, except with reactive metals (K Na Li Mg) in which case H2 gas is produced plus a solution of metal hydroxide

Question 20

Rules of electrolysis: anode

Answer 20

Non metal, except sulphates in which case O2

Question 21

Electroplating

Answer 21

You put what you want to electroplate at the cathode (as metals go to the cathode) and a layer of metal is electrolysed onto your item. Corrosion resistant and pretty

Question 22

Purify copper

Answer 22

A large lump of impure copper is used at the anode and the cathode is made of pure copper. That’s the anode, instead of anions losing electrons, neutral copper atoms lose electrons to become copper ions ( cu -> cu2+ +2e- ) , they then move through the electrolyte to the cathode where they become copper atoms again ( cu2+ +2e- -> cu ) The anode loses mass as copper atoms leave it and the cathode gains mass as copper atoms join it. The impurities sink to the bottom as a pile of sludge.