Question

$E^{\circ}$ values for the couples $Cr ^{3+} / Cr ^{2+}$ & $Mn ^{3+} / Mn ^{2+}$ are $-0.41$ & $+1.51\, V$ respectively. Considering these values select the correct option:

• A. $Cr ^{2+}$ acts as a reducing agent and $Mn ^{3+}$ acts as an oxidising agent in their aqueous solutions
• B. $Cr ^{2+}_{\text {(aq) }}$ is more stable than $Cr ^{3+}_{(aq)}$
• C. $Mn ^{3+}_{(a q)}$ is more stable than $Mn ^{2+}_{(aq)}$
• D. None of these

Answer 1

Answer: (A)

$Cr ^{2+}$ acts as reducing agent because it is itself oxidised to $Cr ^{3+}$ giving it $t_{ eg }{ }^{3}$ configuration, whereas $Mn ^{3+}$ acts as oxidising agent giving it $3 d ^{5}$ configuration