Comment on each of the given observations : `E^(0)` for `M^(2+) (aq) + 2e to M(s)` (where M = Ca, Sr or Ba) is nearly constant.

Explanation

`M^(2+) (aq) + 2e to M (s)` [where M = Ca, Sr, Ba ]
Standard electrode potential `CO_3^(2-)` depends on 3 factors-(a) Enthalpy of vaporisation, (b) ionisation enthalpy and (c) enthalpy of hydration. As the combined effect of these factors is almost same for Ca, Sr and Ba, their `E^(0)` values are nearly constant.