Question

Ferrous ions can be oxidised by which of the following ions?
(A) $L{{i}^{+}}$
(B) $M{{n}^{2+}}$\[\]
(C) $A{{g}^{+}}$
(D) $A{{l}^{3+}}$

Answer 1

Hint: An attempt to this question can be made by determining the state in which the element is stable. In the given options, determine the ion that when reduced is more stable than the current state. The electrochemical reactivity series will help you get a better understanding of the nature of ions and elements.

Complete Solution :
- We will evaluate the nature of ions mentioned in the options as suggested in the hint.
- Lithium is an electropositive metal. It is above iron in the reactivity series and thus cannot be reduced by ferrous ions.
- Manganese in its +2-oxidation state is an excellent reducing agent as it oxidises to +7 state. It is above iron in the electrochemical reactivity series.
- Silver ion is below iron in the electrochemical reactivity. Thus, it can oxidise ferrous ions in an aqueous solution.
- Aluminium is an electropositive metal. It is stable in its +3-oxidation state due to completion of octet. -Also, it is above iron in the reactivity series. Hence it cannot oxidise ferrous ions in an aqueous solution.
- From the above evaluation, we can conclude that ferrous ions can be oxidised by silver ions.
So, the correct answer is “Option C”.

Note: The stability of an ion can be determined by looking at its electronic configuration. An ion undergoes oxidation/reduction only when it hasn’t yet attained the stable octet configuration. Based on this you can reason the oxidising/reducing character observed in few ions.