Changing the surface area of the reactants
3 marks · NormalA student conducts two experiments: - Experiment 1: 5.0 g of marble chips (large lumps) - Experiment 2: 5.0 g marble powder Both react with identical volumes and concentrations of dilute hydrochloric acid at the same temperature. In Experiment 1, all the marble has reacted in 7 minutes. In Experiment 2, the reaction is complete in 2 minutes.
Calculate the average rate of reaction in grams of marble reacted per minute for: (a) Experiment 1 (b) Experiment 2.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Experiment 1: 0.71 g/min; Experiment 2: 2.5 g/min. g/min (±0.01)
Must show: Correct calculation for each experiment
Also accept: Values rounded to 2 decimal places
Common mistakes: Mixing up which time goes with which experiment
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Selects correct method: rate = mass/time for each experiment.
A1 · 1 mark · Correctly calculates rate for Experiment 1: 5.0/7 = 0.71 (to 2 dp) g/min.
A2 · 1 mark · Correctly calculates rate for Experiment 2: 5.0/2 = 2.5 g/min.
Worked solution
Average rate = total mass/time taken.
Experiment 1: 5.0 g / 7 min = 0.714 g/min (to 2 dp: 0.71 g/min).
Experiment 2: 5.0 g / 2 min = 2.5 g/min.