Reactions of metal ions with sodium hydroxide and ammoniaEdexcel International A Level Chemistry: Mind map

Exam questions on Reactions of metal ions with sodium hydroxide and ammonia

1. A technician has four solutions, each containing one of the ions Cu²⁺(aq), Fe²⁺(aq), Fe³⁺(aq) or Zn²⁺(aq). She adds aqueous sodium hydroxide to a sample of each solution, first dropwise and then in excess.
   State what is seen when sodium hydroxide is added to the Cu²⁺(aq) solution and write an ionic equation for the reaction, using the simple formulae of the species.2 marks
2. Aqueous ammonia is added first dropwise and then in excess to separate solutions of Ni²⁺(aq), Co²⁺(aq) and Cu²⁺(aq). In each case a precipitate forms at first.
   Explain, with an equation, why a precipitate forms when a few drops of aqueous ammonia are added to Cu²⁺(aq).2 marks
3. Aqueous chromium(III) ions, Cr³⁺(aq), are green and aqueous zinc ions, Zn²⁺(aq), are colourless. A student adds sodium hydroxide solution to each, first dropwise and then in excess, and later adds dilute sulfuric acid to the precipitates.
   Describe what is seen when sodium hydroxide solution is added, first dropwise and then in excess, to the Cr³⁺(aq) solution.3 marks