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.
[6 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A coastal authority receives projections of sea-level rise between 0.25 m and 0.70 m by a stated date. The range reflects different future emissions and model uncertainty.
Explain why the range does not mean that no action is justified, and identify two scientific causes of rising sea level.
[4 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
An equilibrium mixture follows P+Q⇌R in solution. A process continuously removes R while fresh P and Q are supplied. Temperature is constant.
Explain why product removal can increase the total amount of R collected, and why this is not evidence that the equilibrium reaction has become irreversible.
[4 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.
