Derive the Nernst equation for calculating $E_{cell}$ of a Daniell cell and explain the effect on $E_{cell}$ when there is a change in the concentration of $Zn^{2+}$ and $Cu^{2+}$ ions.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) For the Daniell cell reaction: $Zn_{(s)} + Cu_{(aq)}^{2+} \rightarrow Zn_{(aq)}^{2+} + Cu_{(s)}$
The Nernst equation for the cell potential is given by:
$E_{cell} = E_{cell}^{\emptyset} - \frac{RT}{nF} \ln Q$
Where $Q = \frac{[Zn^{2+}]}{[Cu^{2+}]}$ and $n = 2$ (number of electrons transferred).
Substituting the values:
$E_{cell} = E_{cell}^{\emptyset} - \frac{RT}{2F} \ln \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Converting to $\log_{10}$ at $298 \ K$:
$E_{cell} = E_{cell}^{\emptyset} - \frac{0.0591}{2} \log_{10} \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Effect of concentration changes:
$1$. If the concentration of $Cu^{2+}$ increases,the ratio $\frac{[Zn^{2+}]}{[Cu^{2+}]}$ decreases,making the logarithmic term smaller,which increases $E_{cell}$.
$2$. If the concentration of $Zn^{2+}$ increases,the ratio $\frac{[Zn^{2+}]}{[Cu^{2+}]}$ increases,making the logarithmic term larger,which decreases $E_{cell}$.

Explore More

Similar Questions

The reduction potential of a hydrogen half-cell will be negative if:

The hydrogen electrode is dipped in a solution of $pH=3$ at $25^{\circ} C$. The potential of the electrode will be . . . . . . $\times 10^{-2} \ V$. $\left(\frac{2.303 RT}{F}=0.059 \ V\right)$

The Gibbs energy change of the reaction (in $kJ \ mol^{-1}$) corresponding to the following cell $Cr | Cr^{3+} (0.1 \ M) || Fe^{2+} (0.01 \ M) | Fe$ is: (Given: $E^{\circ}_{Cr^{3+}/Cr} = -0.74 \ V$,$E^{\circ}_{Fe^{2+}/Fe} = -0.44 \ V$)

The equilibrium constant for the following general reaction is $10^{30}$. Calculate $E^{o}$ for the cell at $298 \ K$ ............ $V$
$2X_{2(s)} + 3Y^{2+}_{(aq)} \to 2{X_{2}}^{3+}_{(aq)} + 3Y_{(s)}$

Calculate the cell potential at $298 \ K$ for the following cells:
$(a)$ $Cd \mid Cd^{2+}(0.02 \ M) \parallel H^{+}(1 \ M) \mid H_{2(g)}(1 \ bar) \mid Pt$ $\left[ E_{Cd^{2+} \mid Cd}^0 = -0.40 \ V \right]$
$(b)$ $Al \mid Al^{3+}(0.25 \ M) \parallel Zn^{2+}(0.15 \ M) \mid Zn_{(s)}$ $\left[ E_{Al^{3+} \mid Al}^0 = -1.66 \ V, E_{Zn^{2+} \mid Zn}^0 = -0.76 \ V \right]$

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo