Reactions of metals with dilute acids
2 marks · EasyA student reacts 0.010 mol of zinc powder with 50 cm³ of dilute hydrochloric acid. The initial temperature is 20 °C and the maximum temperature is 28 °C.
Calculate the temperature rise during the reaction.
Explain, using the data, which metal would be more reactive: zinc (temperature rise 8°C) or iron (temperature rise 4°C, same conditions).
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(a) 8°C
(b) Zinc is more reactive because it causes a greater temperature rise in the reaction under the same conditions.
Common mistakes: Mixing up calculation steps; claiming lower rise means more reactive.
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Marking points
M1 (a) · 1 mark · Correct calculation: 28°C - 20°C = 8°C.
B1 (b) · 1 mark · Identifies zinc as more reactive and explains this is because it gives a higher temperature rise under the same conditions.
Worked solution
a) Temperature rise = Maximum temperature - Initial temperature = 28°C - 20°C = 8°C.
b) Zinc is more reactive than iron because its reaction causes a higher temperature rise (8°C vs 4°C) with the acid, so it gives out more heat and reacts more vigorously under the same conditions.