2.5 Electrolysis

Question 1

Electrolysis

Answer 1

Splitting up using electricity
OR
The chemical decomposition by passing electricity through a liquid or solution with ions in

Question 2

What are electrodes usually made off?

Answer 2

An unreactive or inert substance e.g graphite or platinum

Question 3

Can covalent compounds be electrolysed?

Answer 3

Cannot usually unless they react in water to form ions e.g acids in water

Question 4

Why does the whole circuit keep working even though no electrons pass through the electrolyte in the beaker?

Answer 4

Because the ions transfer charge to continue the circuit. Eventually the circuit will stop when the solution/ electrolyte has run out/ electrolysed!

Question 5

An electrode

Answer 5

An electrical conductor through which electricity enters or leaves a non-metallic object or substance e.g electrolyte

Question 6

Anode

Answer 6

Positively charged electrode

Question 7

Cathode

Answer 7

Negatively charged electrode

Question 8

Electrolyte

Answer 8

A liquid or gel which contains ions and can be decomposed by electrolytes.

Question 9

Electrolysis

Answer 9

Chemical decomposition produced by passing en electric current through a liquid or solution containing ions.

Question 10

An ion

Answer 10

An atom or molecule with a charge due to the loss or gain of one or more electrons.

Question 11

Compounds

Answer 11

Composed of 2 or more separate elements bonded together; a mixture

Question 12

Diatomic atoms

Answer 12

Nitrogen
Hydrogen
Oxygen
Iodine
Bromine

Question 13

How are chloride, bromide or iodide discharged at the positive electrode.

Answer 13

As chlorine, bromine or iodine.

Question 14

What happens at the NEGATIVE ELECTRODE?

Answer 14

More reactive positive ions stay in solution, less reactive are discharged( lose charge go to electrode).

Question 15

What happens at the POSITIVE ELECTRODE?

Answer 15

Order of discharge- halide> hydroxide ( when hydroxide ions are discharged, oxygen is given off)> all other negative charged ions.

Question 16

Halogens

Answer 16

What elements in group 7 are known as and when charged called halides.

Question 17

Oxidation

Answer 17

Loss of electrons (OIL RIG)

Question 18

Reduction

Answer 18

Is gain of electrons (OIL RIG)

Question 19

What are redox reactions?

Answer 19

Both reduction and oxidation take place.
E.g
PbBr2 👉 Pb + Br2

Question 20

What would a half equation for a positive electrode look like?

Answer 20

2Br- 👉 Br2 + 2e-

Question 21

What would a half equation for a negative electrode look like?

Answer 21

Pb2+ + 2e- 👉 Pb

Question 22

What is brine?

Answer 22

A solution of sodium chloride in water (NaCl dissolved in H2O)

Question 23

Test for hydrogen?

Answer 23

Squeaky ‘pop’ test, if place a burning splint into hydrogen gas, will make a ‘pop’ sound.

Question 24

Test for chlorine

Answer 24

Turns blue litmus paper red then bleached white.

Question 25

Hydrogen in industry?

Answer 25

Primarily used as a reactant, but also a fuel in space. ``` Also used in; Fertiliser and paint industries Fuel cells Food and chemical industries Electrical generators Methanol production ```

Question 26

Chlorine in industry?

Answer 26

``` Commonly used to make drinking water safe and to treat swimming pools, also used as an antiseptic. Also used in ; Production of paper products Plastics Dyes Textiles Medicines Solvents Paints ```

Question 27

Sodium hydroxide industry?

Answer 27

``` A very common base used in the chemical industry, used drain and oven cleaners, oil refining, water treatment and metal processing. Also used in manufacture of; Fabric Plastic wrap Paper Soap ```

Question 28

Some examples of electroplating?

Answer 28

Chromium- plated kettle Chromium- plated handlebars (bikes) Tin-plated steel can Gold/silver plated jewellery

Question 29

Oxidation

Answer 29

Loss of electrons (OIL RIG)

Question 30

Reduction

Answer 30

Is gain of electrons (OIL RIG)

Question 31

What are redox reactions?

Answer 31

Both reduction and oxidation take place. E.g PbBr2 👉 Pb + Br2

Question 32

What would a half equation for a positive electrode look like?

Answer 32

2Br- 👉 Br2 + 2e-

Question 33

What would a half equation for a negative electrode look like?

Answer 33

Pb2+ + 2e- 👉 Pb

Question 34

What is brine?

Answer 34

A solution of sodium chloride in water (NaCl dissolved in H2O)

Question 35

Test for hydrogen?

Answer 35

Squeaky 'pop' test, if place a burning splint into hydrogen gas, will make a 'pop' sound.

Question 36

Test for chlorine

Answer 36

Turns blue litmus paper red then bleached white.

Question 37

Hydrogen in industry?

Answer 37

Primarily used as a reactant, but also a fuel in space. ``` Also used in; Fertiliser and paint industries Fuel cells Food and chemical industries Electrical generators Methanol production ```

Question 38

Chlorine in industry?

Answer 38

``` Commonly used to make drinking water safe and to treat swimming pools, also used as an antiseptic. Also used in ; Production of paper products Plastics Dyes Textiles Medicines Solvents Paints ```

Question 39

Sodium hydroxide industry?

Answer 39

``` A very common base used in the chemical industry, used drain and oven cleaners, oil refining, water treatment and metal processing. Also used in manufacture of; Fabric Plastic wrap Paper Soap ```

Question 40

Some examples of electroplating?

Answer 40

Chromium- plated kettle Chromium- plated handlebars (bikes) Tin-plated steel can Gold/silver plated jewellery

Question 41

Why do we electroplate?

Answer 41

Protect metal beneath from eroding. More attractive. Increase hardness and its resistance to scratching. Saves money by using a thin layer of a precious metal instead of the pure expensive metal. Helps people allergic to nickel- a metal often used to make cheap jewellery.

Question 42

An electroplated object is..

Answer 42

Coated with a thin layer of metal by electrolysis.