If more than one species is available near the cathode,which species will undergo a reduction reaction? Provide suitable examples.
(N/A) When multiple species are available for reduction at the cathode,the species with the higher (more positive) standard electrode potential $(E^\circ)$ will be reduced preferentially.
This is because a higher $E^\circ$ value indicates a greater tendency to gain electrons.
Example: In an aqueous solution of $NaCl$,both $Na^+$ ions and $H_2O$ molecules are present near the cathode.
The reduction potentials are:
$Na^+ + e^- \rightarrow Na$ $(E^\circ = -2.71 \ V)$
$2H_2O + 2e^- \rightarrow H_2(g) + 2OH^-(aq)$ $(E^\circ = -0.83 \ V)$
Since $-0.83 \ V > -2.71 \ V$,water molecules are reduced at the cathode instead of $Na^+$ ions,resulting in the evolution of $H_2$ gas.
This is because a higher $E^\circ$ value indicates a greater tendency to gain electrons.
Example: In an aqueous solution of $NaCl$,both $Na^+$ ions and $H_2O$ molecules are present near the cathode.
The reduction potentials are:
$Na^+ + e^- \rightarrow Na$ $(E^\circ = -2.71 \ V)$
$2H_2O + 2e^- \rightarrow H_2(g) + 2OH^-(aq)$ $(E^\circ = -0.83 \ V)$
Since $-0.83 \ V > -2.71 \ V$,water molecules are reduced at the cathode instead of $Na^+$ ions,resulting in the evolution of $H_2$ gas.
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Similar Questions
For the given reactions:
$Sn^{2+} + 2e^{-} \rightarrow Sn$
$Sn^{4+} + 4e^{-} \rightarrow Sn$
The electrode potentials are $E^{\circ}_{Sn^{2+}/Sn} = -0.140 \ V$ and $E^{\circ}_{Sn^{4+}/Sn} = 0.010 \ V$. The magnitude of standard electrode potential for $Sn^{4+}/Sn^{2+}$,i.e.,$E^{\circ}_{Sn^{4+}/Sn^{2+}}$,is $..... \times 10^{-2} \ V$. (Nearest integer)
$Sn^{2+} + 2e^{-} \rightarrow Sn$
$Sn^{4+} + 4e^{-} \rightarrow Sn$
The electrode potentials are $E^{\circ}_{Sn^{2+}/Sn} = -0.140 \ V$ and $E^{\circ}_{Sn^{4+}/Sn} = 0.010 \ V$. The magnitude of standard electrode potential for $Sn^{4+}/Sn^{2+}$,i.e.,$E^{\circ}_{Sn^{4+}/Sn^{2+}}$,is $..... \times 10^{-2} \ V$. (Nearest integer)
Which of the following has the least tendency to liberate $H_2$ from mineral acids?
For the reaction taking place in the cell:
$Pt_{(s)} | H_{2(g)} | H^{+}_{(aq)} || Ag^{+}_{(aq)} | Ag_{(s)}$
$E_{Cell}^0 = +0.5332 \ V$.
The value of $\Delta_f G^0$ in $kJ \ mol^{-1}$ (nearest integer) is:
$Pt_{(s)} | H_{2(g)} | H^{+}_{(aq)} || Ag^{+}_{(aq)} | Ag_{(s)}$
$E_{Cell}^0 = +0.5332 \ V$.
The value of $\Delta_f G^0$ in $kJ \ mol^{-1}$ (nearest integer) is:
The $(\frac{\partial E}{\partial T})_P$ of different types of half cells are as follows:
$A$ $B$ $C$ $D$ $1 \times 10^{-4}$ $2 \times 10^{-4}$ $0.1 \times 10^{-4}$ $0.2 \times 10^{-4}$
(Where $E$ is the electromotive force)
Which of the above half cells would be preferred to be used as reference electrode?
| $A$ | $B$ | $C$ | $D$ |
|---|---|---|---|
| $1 \times 10^{-4}$ | $2 \times 10^{-4}$ | $0.1 \times 10^{-4}$ | $0.2 \times 10^{-4}$ |
(Where $E$ is the electromotive force)
Which of the above half cells would be preferred to be used as reference electrode?
DifficultJEE MAIN 2022
View SolutionCalculate the standard cell potential for a cell having the following reaction: $2 Al_{(s)} + 3 Ni^{2+} \rightarrow 2 Al^{3+} + 3 Ni_{(s)}$ given that $E_{Ni^{2+}/Ni}^{\circ} = -0.25 \ V$ and $E_{Al^{3+}/Al}^{\circ} = -1.66 \ V$. (in $V$)
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