6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Iron is extracted from iron oxide in a blast furnace by heating it with carbon. Aluminium is extracted from aluminium oxide by electrolysis, which uses a large amount of electrical energy.
Explain, using ideas about the reactivity series, why iron can be extracted from its oxide by heating with carbon, but aluminium cannot — so aluminium has to be extracted by electrolysis instead. (6 marks)
A student prepared pure, dry crystals of the soluble salt copper sulfate by reacting an excess of solid copper oxide (an insoluble base) with dilute sulfuric acid.
The word equation is: copper oxide + sulfuric acid → copper sulfate + water
(a) Describe how the student should carry out this preparation to obtain pure, dry copper sulfate crystals, including how they make sure all the acid has reacted and how they separate the unreacted copper oxide. (3 marks)
(b) Write the balanced symbol equation, including state symbols, for the reaction. The formulae are: copper oxide CuO, sulfuric acid H₂SO₄, copper sulfate CuSO₄. (1 mark)
Molten lead bromide (PbBr₂) can be broken down by electrolysis. During the process, lead metal forms at one electrode and bromine forms at the other.
(a) At which electrode (the positive or the negative) is the lead produced, and why does the lead form there? (2 marks)
(b) Explain why lead bromide must be molten (or dissolved) before it will conduct electricity and be electrolysed. (1 mark)
The pH scale is used to measure how acidic or alkaline a solution is.
(a) Hydrochloric acid and ethanoic acid both have the same concentration, but hydrochloric acid has a lower pH. Hydrochloric acid is a strong acid and ethanoic acid is a weak acid. Explain, in terms of ionisation, why the strong acid has the lower pH. (2 marks)
(b) Write the ionic equation, including state symbols, for the neutralisation reaction that occurs when any acid reacts with any alkali in solution. (1 mark)
When magnesium reacts with dilute hydrochloric acid, the following reaction occurs:
Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
In this reaction the magnesium is oxidised.
Explain, in terms of electrons, what is meant by saying the magnesium is oxidised. (2 marks)
Universal indicator is added to a solution and turns green, showing the solution has a pH of 7.
State whether a solution with a pH of 7 is acidic, alkaline or neutral. (1 mark)