The reactivity ladder shows four metals. A student adds each metal in turn to iron(II) sulfate solution. Only the metals more reactive than iron will produc...
Question 1 Report
The reactivity ladder shows four metals. A student adds each metal in turn to iron(II) sulfate solution. Only the metals more reactive than iron will produce a coating of iron. How many of the four metals shown produce a coating?
Answer Details
A metal displaces iron from iron(II) sulfate only if it is above iron in the series, because it must be able to give electrons to \( \text{Fe}^{2+} \) ions: \( \text{M} + \text{FeSO}_4 \rightarrow \text{MSO}_4 + \text{Fe} \).
Reading the ladder, calcium, magnesium and zinc all sit above the iron line, so each deposits a coating of iron. Copper is printed below iron, so it cannot reduce \( \text{Fe}^{2+} \) and no coating appears. That gives three metals producing a coating.
Counting four is the usual error, from assuming every metal added must do something. In practice calcium also attacks the water itself, so its coating is masked by fizzing, but by series position it still qualifies.
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