The standard reduction potentials at $$298\,K$$ for the following half reactions are given against each
$$\eqalign{
& Z{n^{2 + }}\left( {aq} \right) + 2{e^ - } \rightleftharpoons Zn\left( s \right);\,\, - 0.762\,V \cr
& C{r^{3 + }}\left( {aq} \right) + 3{e^ - } \rightleftharpoons Cr\left( s \right);\,\, - 0.740\,V \cr
& 2{H^ + }\left( {aq} \right) + 2{e^ - } \rightleftharpoons {H_2}\left( g \right);\,\,0.00\,V \cr
& F{e^{3 + }}\left( {aq} \right) + {e^ - } \rightleftharpoons F{e^{2 + }}\left( {aq} \right);\,\,0.770\,V \cr} $$
Which is the strongest reducing agent ?
A.
$$Zn\left( s \right)$$
B.
$$Cr\left( s \right)$$
C.
$${H_2}\left( g \right)$$
D.
$$F{e^{3 + }}\left( {aq} \right)$$
Answer :
$$Zn\left( s \right)$$
Solution :
Since oxidation potential of $$Zn$$ is highest hence strongest reducing agent.
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 :