Question

On the basis of electrochemical series, how would you predict thermal stability of oxides of different metals?

Answer 1

1. Thermal stability of oxides can be predicted by knowing the standard reduction potential (E°) of the corresponding metals using the electrochemical series.
2. Metals with low or negative standard reduction potentials (i.e., placed above in the electrochemical series) are more electropositive and form more stable oxides.
3. As we move down the electrochemical series, the electropositive character of metals decreases, and hence the thermal stability of their oxides also decreases.
4. Oxides of metals with high negative E° values (e.g., K, Ca, Na) are thermally stable.
5. Oxides of metals with high positive E° values (e.g., Ag, Au) are less stable towards heat and decompose easily on heating.
6. So, by knowing the position of a metal in the electrochemical series, we can predict the thermal stability of its oxide.