CHEMISTRY 5070 · STRUCTURED PRACTICE
A student investigates two processes involving calcium and silver compounds: • Process A: Dissolving solid calcium chloride in water: → . The solution warms up. • Process B: Exposing photographic paper coated with silver bromide, AgBr, to sunlight. The pale yellow coating turns dark grey.
Distinguish Process A from Process B in terms of whether they are physical or chemical changes. Justify your answer for each process.
Process B is a photochemical redox reaction: 2AgBr(s) → 2Ag(s) +
Write the ionic half-equation for the reduction of silver ions to silver metal.
Identify the species oxidised and explain the change in its oxidation number.
The student heats 10.0 g of calcium carbonate, , in an open crucible: → CaO(s) +
Explain why the mass of solid remaining in the open crucible decreases, and state how the law of conservation of mass applies to this reaction.
Suggest how the experiment could be modified to demonstrate that total mass is conserved.
Total: 9 marks