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]
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]
7 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A student measures a beaker as 42.36 g empty and 47.82 g with a dry solid. Each balance reading has uncertainty ±0.01 g. Add absolute uncertainties for a mass found by subtraction.
.1
Calculate the mass of solid.
[2 marks]
.2
Calculate the percentage uncertainty in the solid mass.
[3 marks]
.3
Suggest how a larger mass of the same solid affects percentage uncertainty with this balance.
[2 marks]
6 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
Two separate samples each have mass 8.0 g. One is oxygen gas, O2, and the other is sulfur dioxide, SO2.Ar: O = 16, S = 32.
.1
Calculate the amount of oxygen molecules in the oxygen sample.
[2 marks]
.2
Calculate the amount of sulfur dioxide molecules in its sample.
[2 marks]
.3
Explain which sample contains more molecules and by what factor.
[2 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A polymer model contains 150 chains. Each chain contains 400 repeat units.
.1
Calculate the total number of repeat units represented.
[2 marks]
.2
Explain why this model represents a polymer rather than a giant covalent lattice.
