CAIE A-Level Chemistry Practical Assessment Skills

Aqueous bromine reacts with methanoic acid to form hydrogen bromide and carbon dioxide gas.

The table shows the oxidation numbers of bromine and carbon in the species involved in this reaction.

Suggest one change you would observe, ignoring temperature changes, when bromine reacts with methanoic acid.

The reaction between $\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq})$ and HCl(aq) is monitored at constant temperature.

Fig. 4.1 shows how the concentration of HCl(aq) varies with time.

Explain why the rate of reaction cannot be monitored accurately by measuring the volume of $\mathrm{SO}_{2}(\mathrm{~g})$ produced in this reaction.

Compound T is a white crystalline solid.
When a sample of compound T is mixed with aqueous sodium hydroxide and heated, a gas is produced which turns damp red litmus paper blue.

Further testing of a solution of compound T with aqueous barium chloride produces a dense white precipitate which does not dissolve when dilute hydrochloric acid is added to the mixture.

What is the identity of compound T ?

When dealing with a spillage of metallic sodium it is important that no toxic or flammable products are formed.

Which material should be used if there is a spillage of metallic sodium?