Reactions of metals with dilute acids
3 marks · EasyThe table shows the maximum temperatures reached when equal moles of different metals react with excess dilute hydrochloric acid.
| Metal | Initial temperature / °C | Maximum temperature / °C |
|---|---|---|
| Aluminium | 18 | 29 |
| Zinc | 18 | 23 |
| Iron | 18 | 20 |
| Copper | 18 | 18 |
Calculate the temperature change for zinc.
Which metal was the least reactive? Use data to support your answer.
Explain why the reaction with aluminium may need to be warmed before it proceeds quickly.
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.
Show answer
(a) 5 °C · must show 23 - 18 = 5
(b) Copper; no temperature change/temperature remained at 18°C · must show Copper, cites 18°C as evidence
(c) Aluminium has a strong oxide layer which stops acid reacting quickly unless warmed. · must show Oxide layer acts as barrier
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct calculation: 23 - 18 = 5 (°C)
B1 (b) · 1 mark · Correctly identifies copper as least reactive, with relevant temperature data.
B2 (c) · 1 mark · Explains that aluminium’s oxide layer must be removed by warming to allow reaction.
Worked solution
a) Temperature change for zinc = 23 - 18 = 5°C
b) Copper is the least reactive, as its temperature remained constant at 18°C.
c) Aluminium is coated in a thin oxide layer, so the acid cannot react until this layer is removed by warming.