Identify the correct order of increasing reducing strength of...

Reducing strength of a metal depends on its tendency to lose electrons, which is inversely proportional to its standard reduction potential (E^{{}^{\circ}}$).<br><br>A lower (more negative) standard reduction potential indicates a stronger reducing agent.<br><br>The standard reduction potentials (E^{{}^{\circ}}$) for the given metals are:
$E^{{}^{\circ}}_{\text{Li}^{+} / \text{Li}} = -3.05 \text{ V}$
$E^{{}^{\circ}}_{\text{Mg}^{2+} / \text{Mg}} = -2.36 \text{ V}$
$E^{{}^{\circ}}_{\text{Ni}^{2+} / \text{Ni}} = -0.25 \text{ V}$
$E^{{}^{\circ}}_{\text{Ag}^{+} / \text{Ag}} = +0.80 \text{ V}$

Since the reduction potential increases in the order $\text{Li} < \text{Mg} < \text{Ni} < \text{Ag}$, the reducing strength increases in the reverse order.

Thus, the correct order of increasing reducing strength is $\text{Ag} < \text{Ni} < \text{Mg} < \text{Li}$.

Answer: Ag < Ni < Mg < Li