The diagram shows powdered metal being tipped into dilute acid and the gas collected over water in a measuring cylinder. Using the reactivity series, which ...
Question 1 Report
The diagram shows powdered metal being tipped into dilute acid and the gas collected over water in a measuring cylinder. Using the reactivity series, which metal would give the SLOWEST rate of gas collection?
Answer Details
The volume of gas collected per minute follows the metal's position in the reactivity series: the higher the metal, the faster hydrogen bubbles off into the measuring cylinder.
Ranking the four given metals from the series gives calcium highest, then magnesium, then zinc, with iron lowest. Iron therefore reacts most sluggishly with dilute acid and gives the slowest rate of gas collection: \( \text{Fe} + 2\text{HCl} \rightarrow \text{FeCl}_2 + \text{H}_2 \).
Calcium is a tempting wrong choice for "slow" because it feels less familiar than magnesium, but calcium is a Group II metal that reacts even with cold water, so with acid it is violently fast. Rank by series position, not by how often the metal appears in lessons.
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