Changing the surface area of the reactants
4 marks · NormalThe table shows the total volume of gas produced over time when excess hydrochloric acid reacts separately with two forms of zinc of the same mass: powder and large granules.
| Time (min) | Zinc powder (cm³) | Zinc granules (cm³) |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 38 | 15 |
| 2 | 65 | 25 |
| 3 | 85 | 32 |
| 4 | 90 | 39 |
| 5 | 90 | 43 |
| 6 | 90 | 44 |
Describe the difference in the rate of reaction between the powder and granules during the first 3 minutes.
Give the total volume of gas produced at the end of both reactions.
Explain why both forms of zinc produced the same final volume of gas.
Explain why the reaction with zinc powder is faster.
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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(a) The powder reacts much faster, shown by the larger increase in gas volume in the first 3 minutes.
(b) Both reactions produce 90 cm³ of gas in total. cm³
(c) Because the same mass of zinc is used in both, so the amount of gas produced is the same regardless of rate.
(d) The powder has a greater surface area so more particles are exposed at once, increasing collision frequency.
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Marking points
D1 (a) · 1 mark · Describes that zinc powder reacts faster, shown by higher volume of gas produced in the same time period.
D2 (b) · 1 mark · Identifies total gas for both as 90 cm³.
D3 (c) · 1 mark · Correct explanation linked to same mass of zinc (same amount of reactant).
D4 (d) · 1 mark · Mentions greater surface area of powder increases frequency of collisions.
Worked solution
a) In 3 minutes, zinc powder produced 85 cm³ gas, granules only 32 cm³. So, powder reacted much faster.
b) Both reactions produce a total of 90 cm³ gas (values at end of table).
c) Both started with the same mass of zinc, so both produce the same amount of gas.
d) Zinc powder has much more surface area, so more particles can react at once.