Reactions of acids
4 marks · NormalThe table shows observations during reactions between different metals and dilute acids:
| Metal | Acid | Observation |
|---|---|---|
| Magnesium | Hydrochloric acid | Rapid fizzing, heat produced, magnesium disappears |
| Iron | Sulfuric acid | Slow fizzing, little heat, iron remains after reaction |
| Zinc | Hydrochloric acid | Moderate fizzing, slow disappearance of metal |
Which metal is the least reactive based on the observations? Give a reason for your answer.
Write a balanced chemical equation for the reaction between magnesium and hydrochloric acid.
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) Iron is least reactive because it reacts the slowest and some iron remains. · must show Identifies iron, Gives reason based on slowest reaction/metal remains
(b) Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g) · must show Balanced equation for Mg+HCl
Common mistakes: Incorrect equation stoichiometry; wrong reasoning about reactivity.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies iron as least reactive.
B2 (a) · 1 mark · Gives a correct reason: slowest reaction or iron does not disappear fully.
B3 (b) · 1 mark · Writes reactants and products correctly in the equation.
B4 (b) · 1 mark · Balances the equation: Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)
Worked solution
a) Iron is the least reactive. It shows slow fizzing and some iron remains, indicating a less vigorous reaction.
b) The balanced equation is: