Name: Fuel Cell
Uploaded: 2019-07-19
Duration: 5 min 7 s
Description: Galvanic cells that are designed to convert the energy of combustion of fuels like hydrogen and methane directly into electrical energy are called fuel cells...

Question

Write the Nernst equation for the cell:

Zn │ {Zn}^{2 +} (1 M) │ │ {Cu}^{2 +} (1 M) │ Cu

where

E °_{{Zn}^{2 +} │ Zn} = ─ 0.76 V

;

E °_{{Cu}^{2 +} │ Cu} = + 0.34 V

. Write the reaction occurring at each of the electrode and its net cell reaction. Also determine its cell potential.

Accepted Answer

In the cell, $Zn │ {Zn}^{2 +} (1 M) │ │ {Cu}^{2 +} (1 M) │ Cu$ , the electrode reactions are,

At anode: $Zn (s) \to {Zn}^{2 +} (aq) + 2 e^{-}$

At cathode: ${Cu}^{2 +} (aq) + 2 e^{-} \to Cu (s)$

Net cell reaction: $Zn (s) + {Cu}^{2 +} (aq) \to {Zn}^{2 +} (aq) + Cu (s)$

The Nernst equation for $Zn │ {Zn}^{2 +} (1 M) │ │ {Cu}^{2 +} (1 M) │ Cu$ cell is,

$E_{cell} = E_{cell}^{0} - \frac{RT}{2 F} \ln \frac{[{Zn}^{2 +} (aq)] [Cu (s)]}{[Zn (s)] [{Cu}^{2 +} (aq)]}$

The concentration of pure metals is taken as constant, and hence,

$E_{cell} = E_{cell}^{0} - \frac{RT}{2 F} \ln \frac{[{Zn}^{2 +} (aq)]}{[{Cu}^{2 +} (aq)]} - - - - - - > (1)$

Where $E_{cell}^{0} = E_{\frac{{Cu}^{2 +}}{Cu}}^{0} - E_{\frac{{Zn}^{2 +}}{Zn}}^{0}$

Therefore, $E_{Cell}^{0} = + 0.34 V - (- 0.76 V) = + 1.10 V$

Given, $[{Zn}^{2 +} (aq)] = 1 M$ and $[{Cu}^{2 +} (aq)] = 1 M$ .

On substituting the values in equation $(1)$ we get,

$E_{cell} = 1.10 - \frac{RT}{2 F} \ln \frac{1}{1}$

Since, $\ln 1 = 0$

$E_{cell} = 1.10 V$

Thus, the cell potential under the given conditions is $1.10 V$ .

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Write the Nernst equation for the cell: Zn│Zn2+1M ││Cu2+1M│Cu where E°Zn2+ │Zn= ─ 0.76V; E°Cu2+ │Cu=+0.34V. Write the reaction occurring at each of the electrode and its net cell reaction. Also determine its cell potential.

Chapter-Wise 3D Chemistry Videos from Embibe Experts EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY

Fuel Cell

Electrolysis of Aqueous Salts Using Inert Electrodes

Electrolysis of Molten Lead Bromide

Learn and Prepare for any exam you want !