Changing the surface area of the reactants
2 marks · EasyA reaction between a solid and a liquid produced 32 cm³ of gas in 4 minutes. When the same mass of solid is powdered and reacted in the same conditions, the reaction is complete in 2 minutes. Calculate the average rate of gas production in both cases. Give your answers in cm³/min and compare the results.
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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Lumps: 8 cm³/min; Powder: 16 cm³/min; Powdered solid has twice the rate of the lump.
Also accept: Powdered sample: 16, Lump: 8
Common mistakes: Using seconds, or incorrect division
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Correct calculation of rate for either case (e.g., 32 ÷ 4 = 8 cm³/min).
A1 · 1 mark · Correctly calculates both rates and compares them (e.g., powdered is double lump).
Worked solution
Lump: 32 cm³ ÷ 4 min = 8 cm³/min.
Powder: 32 cm³ ÷ 2 min = 16 cm³/min.
The powdered solid reacts twice as fast as the lump.