Question

On the basis of electrochemical series, explain why HCl cannot be stored in an aluminium vessel.

Answer 1

According to the electrochemical series, aluminium has a standard electrode potential of E° = −1.66 V, which is much lower than that of hydrogen (E° = 0.00 V). This means aluminium is more reactive than hydrogen and can easily displace hydrogen ions from hydrochloric acid (HCl). As a result, when HCl is stored in an aluminium vessel, a chemical reaction takes place:

\[\ce{2Al_{(s)} + 6HCl_{(aq)} -> 2AlCl3_{(aq)} + 3H2_{(g)}}\]

This reaction corrodes the aluminium and releases hydrogen gas. Therefore, due to this reactivity, HCl cannot be stored in an aluminium vessel.