Changing the concentration of the reactants
2 marks · NormalA reaction between powdered magnesium and dilute hydrochloric acid releases 0.30 g of hydrogen in the first 20 seconds. Calculate the average rate of production of hydrogen gas in g/s.
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0.015 g/s (±0.001)
Common mistakes: Using incorrect formula
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Marking points
M1 · 1 mark · Uses formula rate = mass produced / time. (follow-through)
A1 · 1 mark · Correct answer: 0.015 g/s, to 2 or 3 significant figures. (follow-through)
Worked solution
Average rate = 0.30 / 20 = 0.015 g/s.