QBManager

CHXII03:ELECTROCHEMISTRY

329974 The standard emf of the cell, \(\left. {{\rm{Cd(s)}}} \right \vert \left. {{\rm{CdC}}{{\rm{l}}_{\rm{2}}}{\rm{(aq)}}} \right\vert \left. {{\rm{AgCl(s)}}} \right \vert {\rm{Ag(s)}}\) in which the cell reaction is,
\[\begin{array}{l}
{\rm{Cd}}({\rm{s}}) + {\rm{2AgCl}}({\rm{s}}) \to \\
{\rm{2Ag}}({\rm{s}}) + {\rm{C}}{{\rm{d}}^{{\rm{2 + }}}}({\rm{aq}}) + {\rm{2C}}{{\rm{l}}^ - }({\rm{aq}})
\end{array}\] is \({\rm{0}}{\rm{.6915}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{0^\circ C}}{\mkern 1mu} \) and \({\rm{0}}{\rm{.6753}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{25}}^\circ {\rm{C}}\). The \({\rm{\Delta H}}\) reaction at \({\rm{25^\circ C}}\) is

1 – 167.26 kJ

2 – 176 kJ

3 + 123.5 kJ

4 – 234.7 kJ

CHXII03:ELECTROCHEMISTRY

329975 The standard emf for the given cell reaction, \(\mathrm{Zn}+\mathrm{Cu}^{2+} \rightarrow \mathrm{Cu}+\mathrm{Zn}^{2+}\) is \(1.10 \mathrm{~V}\) at \(25^{\circ} \mathrm{C}\). The emf for the cell reaction, when \(0.1{\text{M C}}{{\text{u}}^{2 + }}\) and \(0.1{\text{M Z}}{{\text{n}}^{2 + }}\) solutions are used at \(25^{\circ} \mathrm{C}\) is

1 \(1.10 \mathrm{~V}\)

2 \(-1.10 \mathrm{~V}\)

3 \(2.20 \mathrm{~V}\)

4 \(-2.20 \mathrm{~V}\)

AIIMS - 2012

CHXII03:ELECTROCHEMISTRY

329976 Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :
Then the species undergoing disproportionation is
supporting img

1 \({\rm{B}}{{\rm{r}}_{\rm{2}}}\)

2 \({\rm{HBrO}}\)

3 \({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\)

4 \({\rm{BrO}}_{\rm{3}}^{\rm{ - }}\)

Explanation:

\(\frac{{\begin{array}{*{20}{l}}{{\rm{2}}\left( {{\rm{BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}}} \right){{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.82}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}} \to {\rm{HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{3BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{2BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.32V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\(\frac{{\begin{array}{*{20}{l}}{{\rm{1/2B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + 1/2B}}{{\rm{r}}_{\rm{2}}}{\rm{ + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 1}}{\rm{.0652V}}}\end{array}}}{{{\rm{B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.5268V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\) never undergoes disproportion reaction
\[\frac{{\begin{array}{*{20}{l}}{{\rm{HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\
{{\rm{4}}\left( {{\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}_{\rm{2}}}} \right){\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{5HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4B}}{{\rm{r}}_{\rm{2}}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 0}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}}\]
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is positive, reaction is spontaneous.

NEET - 2018

CHXII03:ELECTROCHEMISTRY

329977 If \({\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}} \right \vert {\rm{Fe}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.441V}}\,\,{\rm{and}}\,\,{\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}} \right \vert {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.771V}}\), the standard EMF of the reaction, \({\rm{Fe + 2F}}{{\rm{e}}^{{\rm{3 + }}}}{\rm{3F}}{{\rm{e}}^{{\rm{2 + }}}}\) will be

1 \({\rm{1}}{\rm{.653 V}}\)

2 \({\rm{1}}{\rm{.212 V}}\)

3 \({\rm{0}}{\rm{.111 V}}\)

4 \({\rm{ - 0}}{\rm{.330 V}}\)

CHXII03:ELECTROCHEMISTRY

329974 The standard emf of the cell, \(\left. {{\rm{Cd(s)}}} \right \vert \left. {{\rm{CdC}}{{\rm{l}}_{\rm{2}}}{\rm{(aq)}}} \right\vert \left. {{\rm{AgCl(s)}}} \right \vert {\rm{Ag(s)}}\) in which the cell reaction is,
\[\begin{array}{l}
{\rm{Cd}}({\rm{s}}) + {\rm{2AgCl}}({\rm{s}}) \to \\
{\rm{2Ag}}({\rm{s}}) + {\rm{C}}{{\rm{d}}^{{\rm{2 + }}}}({\rm{aq}}) + {\rm{2C}}{{\rm{l}}^ - }({\rm{aq}})
\end{array}\] is \({\rm{0}}{\rm{.6915}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{0^\circ C}}{\mkern 1mu} \) and \({\rm{0}}{\rm{.6753}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{25}}^\circ {\rm{C}}\). The \({\rm{\Delta H}}\) reaction at \({\rm{25^\circ C}}\) is

1 – 167.26 kJ

2 – 176 kJ

3 + 123.5 kJ

4 – 234.7 kJ

CHXII03:ELECTROCHEMISTRY

329975 The standard emf for the given cell reaction, \(\mathrm{Zn}+\mathrm{Cu}^{2+} \rightarrow \mathrm{Cu}+\mathrm{Zn}^{2+}\) is \(1.10 \mathrm{~V}\) at \(25^{\circ} \mathrm{C}\). The emf for the cell reaction, when \(0.1{\text{M C}}{{\text{u}}^{2 + }}\) and \(0.1{\text{M Z}}{{\text{n}}^{2 + }}\) solutions are used at \(25^{\circ} \mathrm{C}\) is

1 \(1.10 \mathrm{~V}\)

2 \(-1.10 \mathrm{~V}\)

3 \(2.20 \mathrm{~V}\)

4 \(-2.20 \mathrm{~V}\)

AIIMS - 2012

CHXII03:ELECTROCHEMISTRY

329976 Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :
Then the species undergoing disproportionation is
supporting img

1 \({\rm{B}}{{\rm{r}}_{\rm{2}}}\)

2 \({\rm{HBrO}}\)

3 \({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\)

4 \({\rm{BrO}}_{\rm{3}}^{\rm{ - }}\)

Explanation:

\(\frac{{\begin{array}{*{20}{l}}{{\rm{2}}\left( {{\rm{BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}}} \right){{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.82}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}} \to {\rm{HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{3BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{2BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.32V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\(\frac{{\begin{array}{*{20}{l}}{{\rm{1/2B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + 1/2B}}{{\rm{r}}_{\rm{2}}}{\rm{ + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 1}}{\rm{.0652V}}}\end{array}}}{{{\rm{B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.5268V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\) never undergoes disproportion reaction
\[\frac{{\begin{array}{*{20}{l}}{{\rm{HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\
{{\rm{4}}\left( {{\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}_{\rm{2}}}} \right){\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{5HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4B}}{{\rm{r}}_{\rm{2}}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 0}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}}\]
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is positive, reaction is spontaneous.

NEET - 2018

CHXII03:ELECTROCHEMISTRY

329977 If \({\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}} \right \vert {\rm{Fe}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.441V}}\,\,{\rm{and}}\,\,{\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}} \right \vert {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.771V}}\), the standard EMF of the reaction, \({\rm{Fe + 2F}}{{\rm{e}}^{{\rm{3 + }}}}{\rm{3F}}{{\rm{e}}^{{\rm{2 + }}}}\) will be

1 \({\rm{1}}{\rm{.653 V}}\)

2 \({\rm{1}}{\rm{.212 V}}\)

3 \({\rm{0}}{\rm{.111 V}}\)

4 \({\rm{ - 0}}{\rm{.330 V}}\)

CHXII03:ELECTROCHEMISTRY

329974 The standard emf of the cell, \(\left. {{\rm{Cd(s)}}} \right \vert \left. {{\rm{CdC}}{{\rm{l}}_{\rm{2}}}{\rm{(aq)}}} \right\vert \left. {{\rm{AgCl(s)}}} \right \vert {\rm{Ag(s)}}\) in which the cell reaction is,
\[\begin{array}{l}
{\rm{Cd}}({\rm{s}}) + {\rm{2AgCl}}({\rm{s}}) \to \\
{\rm{2Ag}}({\rm{s}}) + {\rm{C}}{{\rm{d}}^{{\rm{2 + }}}}({\rm{aq}}) + {\rm{2C}}{{\rm{l}}^ - }({\rm{aq}})
\end{array}\] is \({\rm{0}}{\rm{.6915}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{0^\circ C}}{\mkern 1mu} \) and \({\rm{0}}{\rm{.6753}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{25}}^\circ {\rm{C}}\). The \({\rm{\Delta H}}\) reaction at \({\rm{25^\circ C}}\) is

1 – 167.26 kJ

2 – 176 kJ

3 + 123.5 kJ

4 – 234.7 kJ

CHXII03:ELECTROCHEMISTRY

329975 The standard emf for the given cell reaction, \(\mathrm{Zn}+\mathrm{Cu}^{2+} \rightarrow \mathrm{Cu}+\mathrm{Zn}^{2+}\) is \(1.10 \mathrm{~V}\) at \(25^{\circ} \mathrm{C}\). The emf for the cell reaction, when \(0.1{\text{M C}}{{\text{u}}^{2 + }}\) and \(0.1{\text{M Z}}{{\text{n}}^{2 + }}\) solutions are used at \(25^{\circ} \mathrm{C}\) is

1 \(1.10 \mathrm{~V}\)

2 \(-1.10 \mathrm{~V}\)

3 \(2.20 \mathrm{~V}\)

4 \(-2.20 \mathrm{~V}\)

AIIMS - 2012

CHXII03:ELECTROCHEMISTRY

329976 Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :
Then the species undergoing disproportionation is
supporting img

1 \({\rm{B}}{{\rm{r}}_{\rm{2}}}\)

2 \({\rm{HBrO}}\)

3 \({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\)

4 \({\rm{BrO}}_{\rm{3}}^{\rm{ - }}\)

Explanation:

\(\frac{{\begin{array}{*{20}{l}}{{\rm{2}}\left( {{\rm{BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}}} \right){{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.82}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}} \to {\rm{HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{3BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{2BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.32V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\(\frac{{\begin{array}{*{20}{l}}{{\rm{1/2B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + 1/2B}}{{\rm{r}}_{\rm{2}}}{\rm{ + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 1}}{\rm{.0652V}}}\end{array}}}{{{\rm{B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.5268V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\) never undergoes disproportion reaction
\[\frac{{\begin{array}{*{20}{l}}{{\rm{HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\
{{\rm{4}}\left( {{\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}_{\rm{2}}}} \right){\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{5HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4B}}{{\rm{r}}_{\rm{2}}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 0}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}}\]
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is positive, reaction is spontaneous.

NEET - 2018

CHXII03:ELECTROCHEMISTRY

329977 If \({\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}} \right \vert {\rm{Fe}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.441V}}\,\,{\rm{and}}\,\,{\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}} \right \vert {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.771V}}\), the standard EMF of the reaction, \({\rm{Fe + 2F}}{{\rm{e}}^{{\rm{3 + }}}}{\rm{3F}}{{\rm{e}}^{{\rm{2 + }}}}\) will be

1 \({\rm{1}}{\rm{.653 V}}\)

2 \({\rm{1}}{\rm{.212 V}}\)

3 \({\rm{0}}{\rm{.111 V}}\)

4 \({\rm{ - 0}}{\rm{.330 V}}\)

CHXII03:ELECTROCHEMISTRY

329974 The standard emf of the cell, \(\left. {{\rm{Cd(s)}}} \right \vert \left. {{\rm{CdC}}{{\rm{l}}_{\rm{2}}}{\rm{(aq)}}} \right\vert \left. {{\rm{AgCl(s)}}} \right \vert {\rm{Ag(s)}}\) in which the cell reaction is,
\[\begin{array}{l}
{\rm{Cd}}({\rm{s}}) + {\rm{2AgCl}}({\rm{s}}) \to \\
{\rm{2Ag}}({\rm{s}}) + {\rm{C}}{{\rm{d}}^{{\rm{2 + }}}}({\rm{aq}}) + {\rm{2C}}{{\rm{l}}^ - }({\rm{aq}})
\end{array}\] is \({\rm{0}}{\rm{.6915}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{0^\circ C}}{\mkern 1mu} \) and \({\rm{0}}{\rm{.6753}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}{\mkern 1mu} {\mkern 1mu} {\rm{at}}{\mkern 1mu} {\mkern 1mu} {\rm{25}}^\circ {\rm{C}}\). The \({\rm{\Delta H}}\) reaction at \({\rm{25^\circ C}}\) is

1 – 167.26 kJ

2 – 176 kJ

3 + 123.5 kJ

4 – 234.7 kJ

CHXII03:ELECTROCHEMISTRY

329975 The standard emf for the given cell reaction, \(\mathrm{Zn}+\mathrm{Cu}^{2+} \rightarrow \mathrm{Cu}+\mathrm{Zn}^{2+}\) is \(1.10 \mathrm{~V}\) at \(25^{\circ} \mathrm{C}\). The emf for the cell reaction, when \(0.1{\text{M C}}{{\text{u}}^{2 + }}\) and \(0.1{\text{M Z}}{{\text{n}}^{2 + }}\) solutions are used at \(25^{\circ} \mathrm{C}\) is

1 \(1.10 \mathrm{~V}\)

2 \(-1.10 \mathrm{~V}\)

3 \(2.20 \mathrm{~V}\)

4 \(-2.20 \mathrm{~V}\)

AIIMS - 2012

CHXII03:ELECTROCHEMISTRY

329976 Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :
Then the species undergoing disproportionation is
supporting img

1 \({\rm{B}}{{\rm{r}}_{\rm{2}}}\)

2 \({\rm{HBrO}}\)

3 \({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\)

4 \({\rm{BrO}}_{\rm{3}}^{\rm{ - }}\)

Explanation:

\(\frac{{\begin{array}{*{20}{l}}{{\rm{2}}\left( {{\rm{BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}}} \right){{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.82}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}} \to {\rm{HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{3BrO}}_{\rm{3}}^{\rm{ - }} \to {\rm{2BrO}}_{\rm{4}}^{\rm{ - }}{\rm{ + HBrO}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.32V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\(\frac{{\begin{array}{*{20}{l}}{{\rm{1/2B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\{{\rm{ + 1/2B}}{{\rm{r}}_{\rm{2}}}{\rm{ + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 1}}{\rm{.0652V}}}\end{array}}}{{{\rm{B}}{{\rm{r}}_{\rm{2}}} \to {\rm{HBrO + B}}{{\rm{r}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = - 0}}{\rm{.5268V}}}}\)
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is negative so the reaction is non-spontaneous
\({\rm{BrO}}_{\rm{4}}^{\rm{ - }}\) never undergoes disproportion reaction
\[\frac{{\begin{array}{*{20}{l}}{{\rm{HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4}}{{\rm{e}}^{\rm{ - }}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = - 1}}{\rm{.5}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\\
{{\rm{4}}\left( {{\rm{HBrO + 1}}{{\rm{e}}^{\rm{ - }}} \to {\rm{B}}{{\rm{r}}_{\rm{2}}}} \right){\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {{\rm{E}}^{\rm{o}}}{\rm{ = 1}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}\end{array}}}{{{\rm{5HBrO}} \to {\rm{BrO}}_{\rm{3}}^{\rm{ - }}{\rm{ + 4B}}{{\rm{r}}_{\rm{2}}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{E}}_{{\rm{cell}}}^{\rm{o}}{\rm{ = 0}}{\rm{.595}}{\mkern 1mu} {\mkern 1mu} {\rm{V}}}}\]
\({\rm{E}}_{{\rm{cell}}}^{\rm{o}}\) is positive, reaction is spontaneous.

NEET - 2018

CHXII03:ELECTROCHEMISTRY

329977 If \({\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}} \right \vert {\rm{Fe}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.441V}}\,\,{\rm{and}}\,\,{\rm{E}}_{\left. {{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}} \right \vert {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}}^{\rm{^\circ }}{\rm{ = - 0}}{\rm{.771V}}\), the standard EMF of the reaction, \({\rm{Fe + 2F}}{{\rm{e}}^{{\rm{3 + }}}}{\rm{3F}}{{\rm{e}}^{{\rm{2 + }}}}\) will be

1 \({\rm{1}}{\rm{.653 V}}\)

2 \({\rm{1}}{\rm{.212 V}}\)

3 \({\rm{0}}{\rm{.111 V}}\)

4 \({\rm{ - 0}}{\rm{.330 V}}\)

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