Chemistry grade 8 exam

The decomposition of an ionic compound, when molten or in aqueous solution,

by the passage of an electric current is the definition of

• electrolyte

• electrolysis

• electrode

• wire

Concentrated aqueous sodium chloride is electrolysed using graphite electrodes.

What is the product formed at the cathode?

• chlorine

• hydrogen

• oxygen

• sodium

What is produced at each electrode during the electrolysis of aqueous solutions

using inert electrodes?

• A

• B

• C

• D

Which substance will not conduct electricity?

• Aluminum

• Copper

• Plastic

• Steel

Which rows identify the electrode products for the named electrolyte?

• 1 and 3

• 1 and 4

• 2 and 3

• 2 and 4

The electrolysis of concentrated hydrochloric acid is shown.

Which statement describes what happens to the electrons during the electrolysis?

• They are added to chloride ions.

• They are added to hydrogen ions.

• They move through the circuit from negative to positive.

• They move through the solution from negative to positive

A student adds a small amount of ammonium chloride to a beaker of water. The

temperature of the water decreases from 21℃ to 17℃. Which type of reaction

has occurred and why?

• A

• B

• C

• D

A reaction pathway diagram is shown.

Which statement about this reaction is correct?

• The reaction rate increases during the reaction.

• The reaction is endothermic.

• The reaction transfers thermal energy to the surroundings.

• The temperature of the surroundings increases.

The reaction pathway diagram for a reaction is shown.

1. The reaction is exothermic.

2. The reaction is endothermic.

3. The temperature of the surroundings increases.

4. The temperature of the surroundings decreases.

Which statements are correct?

• 1 and 3

• 1 and 4

• 2 and 3

• 2 and 4

Hydrogen reacts with oxygen to produce water as shown.

2H–H + O=O →2H–O–H

The reaction causes the surroundings to heat up. Which row identifies the type

of reaction and explains why it is endothermic or exothermic?

• A

• B

• C

• D