These are real past-paper questions. Think of your answer first, then open the explanation.
May/June 2026 · Paper 1 · The Periodic Table
Aqueous bromine is added to aqueous potassium iodide.
Which colour is the aqueous bromine and what is the final colour of the reaction mixture?
- aqueous bromine colourless, final mixture orange
- aqueous bromine colourless, final mixture brown
- aqueous bromine orange, final mixture colourless
- aqueous bromine orange, final mixture brown
Show answer and explanation
Answer: D. aqueous bromine orange, final mixture brown
Aqueous bromine is orange; it displaces iodine from potassium iodide, which gives a brown solution.
Oct/Nov 2025 · Paper 1 · The Periodic Table
The Group I metals lithium, sodium and potassium show trends in their melting points and in their reactions with water. Which statement is correct going down the group from lithium to potassium?
- Their melting points decrease and their reaction with water becomes less vigorous.
- Their melting points decrease and their reaction with water becomes more vigorous.
- Their melting points increase and their reaction with water becomes less vigorous.
- Their melting points increase and their reaction with water becomes more vigorous.
Show answer and explanation
Answer: B. Their melting points decrease and their reaction with water becomes more vigorous.
Going down Group I, the melting points of the metals decrease and their reactivity with water increases, so potassium reacts far more vigorously with water than lithium does.
Oct/Nov 2022 · Paper 1 · The Periodic Table
Noble gases are unreactive because
- full outer shell
- high mass
- metallic
- low boiling point
Show answer and explanation
Answer: A. full outer shell
Stable full outer electron shell.
