CSEC Chemistry · May/June 2010 · Paper 2 · Question 1(a)(iv)

Jonathan and Karen conducted experiments on the decomposition of hydrogen peroxide using manganese(IV) oxide as a catalyst. Jonathan used 100 cm³ of 0.80 mol dm⁻³ hydrogen peroxide, measuring oxygen volume over time (Table 1). Karen used 100 cm³ of 0.40 mol dm⁻³ hydrogen peroxide, with her results shown in Figure 1. The decomposition is exothermic, producing water and oxygen. Figure 2 illustrates the enthalpy change for an exothermic reaction and the effect of a catalyst.

Compare the plots obtained from Jonathan's and Karen's results in terms of the slope of the graph and the volume of oxygen produced. Account for the differences between Jonathan's and Karen's results.

This question uses a figure or table from the paper — you'll see it when you practise.