A plant synthesises a gas by 2X(g)+Y(g)⇌2Z(g). At the same temperature the equilibrium yield rises from 48% at low pressure to 72% at high pressure. The maximum possible product mass is 500 kg.
.1
Calculate the extra mass of Z obtained at high pressure.
[2 marks]
.2
Evaluate whether the increased yield alone proves the high-pressure process is preferable.
[2 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A refinery has 60 tonnes of a long-chain fraction but buyers want only 20 tonnes. Catalytic cracking converts 75% of the 40-tonne surplus into shorter fuel molecules; the rest becomes other useful products.
.1
Calculate the mass of shorter fuel molecules obtained from the surplus.
[2 marks]
.2
Explain why cracking is useful and state one chemical test that distinguishes an alkene product from an alkane.
[2 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
Iron(III) ions are converted to iron(II) ions without forming iron metal.
.1
Write the half equation.
[2 marks]
.2
Calculate the number of electrons needed for 3.0×1020 iron(III) ions.
[2 marks]
.3
Explain why the conversion is reduction even though the product remains positively charged.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Chlorine atoms have electron arrangement 2,8,7. Iodine atoms have more occupied electron shells but also seven outer electrons.
.1
Explain why chlorine is more reactive than iodine.
[3 marks]
.2
Compare this trend with the reactivity trend down group 1.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Students compare two catalysts for the decomposition of hydrogen peroxide. Each trial lasts 60 s; the same solution volume and concentration are available.
Plan an investigation to compare the rates fairly and assess whether a catalyst is used up.
