A student adds an alkali gradually to an acid. The measured pH values after successive additions are 2, 4, 6, 7, 9 and 11.
.1
Describe the change and identify the neutral reading.
[2 marks]
.2
Explain neutralisation in terms of the reacting ions.
[2 marks]
5 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student electrolyses concentrated aqueous potassium chloride using inert electrodes in a teacher-controlled demonstration with suitable ventilation. Potassium is more reactive than hydrogen.
.1
Predict the electrode products and explain the difference from molten potassium chloride.
[3 marks]
.2
Explain how charge is carried through the aqueous electrolyte and through the external metal wires.
[2 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
An aluminium ion becomes an aluminium atom at an electrode. A student says that because aluminium is a reactive metal, this must be oxidation.
.1
Evaluate this statement using electron transfer, electrode identity and charge balance.
[3 marks]
.2
Write the balanced half-equation for this electrode change.
[1 mark]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Propane burns completely in oxygen to form carbon dioxide and water. A sample uses 8.0 g oxygen and produces 6.6 g carbon dioxide and 3.6 g water. No products escape before weighing.
.1
Write the balanced equation for complete combustion of propane, C3H8.
[2 marks]
.2
Calculate the mass of propane that reacted.
[3 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student claims that diamond, graphite and fullerenes have identical properties because all contain only carbon.
Evaluate the claim by connecting structure to properties.
