Given the standard electrode potentials,
K+/K = –2.93V, Ag+/Ag = 0.80V,
Hg2+/Hg = 0.79V
Mg2+/Mg = –2.37V. Cr3+/Cr = –0.74V
arrange these metals in their increasing order of reducing power.
The lower the electrode potential, the stronger is the reducing agent the species is. Therefore, the increasing order of the reducing power of the given metals is Ag < Hg < Cr < Mg < K.