Loading subjects
Oxidation–Reduction · Part 3 of 3
9 exam-style questions with model answers, plus 12 quick multi-choice questions — every question on this part of the standard, grouped by the 3 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
State the colour change you would observe when acidified potassium permanganate is added to a solution containing iron(II) ions, and name the species responsible for each colour.
Hydrogen sulfide gas is bubbled through acidified potassium dichromate solution. Describe the observations and explain them using half equations.
Two colourless solutions are mixed and no visible change occurs; a third colourless solution is then added and the mixture turns brown. Evaluate what can and cannot be concluded from these observations, and explain what further evidence would be needed.
A piece of copper wire is placed in silver nitrate solution. Describe two observations and write the overall ionic equation.
Chlorine water is added separately to potassium bromide and to potassium chloride solutions. Explain what would be observed in each case and what this shows about chlorine.
A student concludes from a single experiment — adding chlorine water to potassium iodide and seeing a brown colour — that chlorine is the strongest oxidant of the halogens. Evaluate this conclusion and describe the minimum set of experiments needed to justify a full order.
List the six components of a complete answer for one redox reaction in this standard.
A student writes: "The solution went from blue to colourless and a brown solid formed. Cu2+ + 2e− → Cu." Explain what is missing for Merit and rewrite the answer so that it would reach Merit.
Explain why, in this standard, an answer containing more correct chemical facts can score lower than an answer containing fewer, and justify what an Excellence answer does differently.