The diagram shows a simple displacement cell in which a more reactive metal loses electrons to a less reactive metal, producing a voltage. Using the reactiv...
Question 1 Report
The diagram shows a simple displacement cell in which a more reactive metal loses electrons to a less reactive metal, producing a voltage. Using the reactivity series, which pairing would give the largest voltage reading?
Answer Details
In a simple cell the voltage depends on how strongly one electrode gives up electrons compared with the other. The bigger the difference in reactivity between the two metals, the further apart their tendencies to lose electrons and the larger the reading on the voltmeter shown in the diagram.
So find the pair that is furthest apart in the reactivity series. Magnesium is high up and copper is low down, a very wide gap, so magnesium paired with copper gives the largest voltage, with magnesium as the negative electrode losing electrons.
\[\mathrm{Mg \rightarrow Mg^{2+} + 2e^-}\]
Iron with tin, lead with copper and copper with silver are all close neighbours in the series, so each gives only a small voltage. Judge these questions by the size of the gap, not by how reactive either single metal is.
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