How many chemical reactions can you identify by using the solution of copper(II) sulfate and solution A
Identify solution A, and see how many reactions you can make.
This session should take one hour.
Materials per group
- Aqueous copper(II) sulfate, 0.25 mol dm–3
- Aqueous ammonium carbonate, 0.25 mol dm–3, labelled A.
Equipment per group
- Test tubes
- Test tube racks
- Glass rods
- pH paper
- Lime water
- Safety glasses
Health, safety and technical notes
- Read our standard health and safety guidance here.
- Wear eye protection.
- This is an open problem and requires the students to exercise care and make careful observations.
One approach is to look at solution A first. On warming, this solution evolves ammonia, which gives the characteristic smell and carbon dioxide.
On mixing solution A with aqueous copper sulfate a blue/green precipitate (Cu(OH)2. CuCO3) is formed initially.
On adding excess A, this dissolves to form a deep blue solution of Cu(NH3)42+(aq).
Evaluation of solution
The best answers are those that identify A, and identify the correct reactions. Some of these can be written as:
- (NH4)2 CO3 (aq) ⇌ 2NH3 (aq) + “H2 CO3 ”(aq)
- (NH4)2 CO3 (aq) ⇌ 2NH4+(aq) + CO32–(aq)
- NH4 +(aq) + H2O(l) ⇌ NH3 (g) + H3O+(aq)
- CO32–(aq) + H2O(l) ⇌ HCO3–(aq) + OH–(aq)
- “H2CO3 ”(aq) ⇌ H2O(l) + CO2 (g)
- Cu2+(aq) + 2OH–(aq) ⇌ Cu(OH)2(s)
- Cu2+(aq) + CO32–(aq) ⇌ CuCO3(s)
- Cu2+(aq) + 4NH3 (aq) ⇌ Cu(NH3)4 2+(aq)
- Ca(OH)2 (s) + CO2 (g) → CaCO3 (s) + H2O(l)
- CaCO3(s) + H2O(l) + CO2 (g) → Ca(HCO3)2 (aq)
This resource is part of a collection of problem-solving activities, designed to engage learners in small group work. Find out how to use these resources, and obtain a list of suggested ‘junk items’ here.
- Experiment | PDF, Size 43.56 kb
The resources were originally published in the book In Search of More Solutions.