Question

On the basis of electrochemical series, explain why Fe can displace hydrogen from dilute HCl but silver cannot.

Answer 1

According to the electrochemical series, metals with lower (more negative) standard reduction potentials are more reactive and can displace hydrogen from dilute acids. Iron (Fe) has a standard electrode potential of E° = −0.44 V, which is lower than that of hydrogen (E° = 0.00 V). This means Fe can lose electrons easily and reduce hydrogen ions (H⁺) to hydrogen gas.

\[\ce{Fe_{(s)} + 2HCl_{(aq)} -> FeCl2_{(aq)} + H2{(g)}}\]

In contrast, silver (Ag) has a higher standard reduction potential (E° = +0.80 V), making it less reactive than hydrogen. As a result, Ag cannot displace hydrogen from dilute HCl. Hence, Fe reacts with HCl to produce hydrogen gas, while Ag does not.