Question

On the basis of electrochemical series, explain why Au₂O₃ decomposes on heating.

Answer 1

According to the electrochemical series, gold (Au) has a very high positive standard reduction potential \[\ce{E_{Au^{3+}/Au}}\] = +1.50 V, which indicates that gold ions have a strong tendency to gain electrons and get reduced to elemental gold. This also means that gold is a very unreactive metal and is thermodynamically unstable in higher oxidation states like in Au₂O₃.

When Au₂O₃ is heated, it decomposes because gold prefers to exist in its elemental form rather than in a combined, oxidised state. The decomposition reaction is:

\[\ce{2Au2O3_{(s)} -> 4Au_{(s)} + 3O2_{(g)}}\]

Thus, based on the electrochemical series, the high position of gold makes Au₂O₃ unstable, and it decomposes on heating to form elemental gold and oxygen.