Standard reduction electrode potentials of three metals $$A, B$$ & $$C$$ are respectively $$+ 0.5 V, -3.0 V$$ & $$-1.2 V.$$ The reducing powers of these metals are
A.
$$A > B > C$$
B.
$$C > B > A$$
C.
$$A > C > B$$
D.
$$B > C > A$$
Answer :
$$B > C > A$$
Solution :
\[\begin{matrix}
A \\
+0.5C \\
\end{matrix}\,\,\,\begin{matrix}
B \\
-3.0V \\
\end{matrix}\,\,\,\begin{matrix}
C \\
-1.2V \\
\end{matrix}\]
NOTE : The higher the negative value of reduction potential, the more is the reducing power.
Hence $$B > C > A.$$
Releted MCQ Question on Physical Chemistry >> Electrochemistry
Releted Question 1
The standard reduction potentials at $$298 K$$ for the following half reactions are given against each
$$\eqalign{
& Z{n^{2 + }}\left( {aq} \right) + 2e \rightleftharpoons Zn\left( s \right)\,\,\,\,\,\,\,\,\, - 0.762 \cr
& C{r^{3 + }}\left( {aq} \right) + 2e \rightleftharpoons Cr\left( s \right)\,\,\,\,\,\,\,\,\, - 0.740 \cr
& 2{H^ + }\left( {aq} \right) + 2e \rightleftharpoons {H_2}\left( g \right)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0.000 \cr
& F{e^{3 + }}\left( {aq} \right) + 2e \rightleftharpoons F{e^{2 + }}\left( {aq} \right)\,\,\,\,\,\,\,\,0.770 \cr} $$
which is the strongest reducing agent ?
A solution containing one mole per litre of each $$Cu{\left( {N{O_3}} \right)_2};AgN{O_3};H{g_2}{\left( {N{O_3}} \right)_2};$$ is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts (reduction potentials) are :
$$\eqalign{
& Ag/A{g^ + } = + 0.80,\,\,2Hg/H{g_2}^{ + + } = + 0.79 \cr
& Cu/C{u^{ + + }} = + 0.34,\,Mg/M{g^{ + + }} = - 2.37 \cr} $$
With increasing voltage, the sequence of deposition of metals on the cathode will be :