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For the following reaction, calculate the equilibrium constant at 25^{\circ}C

Cu\left ( s \right )+2Ag^{+}\left ( aq \right )\rightarrow Cu^{2+}\left ( aq \right )+2Ag\left ( s \right )

Given: E^{\circ}=0.5V,R=8.314\; J/mol.K,\; F=96500\; C

Option: 1

8.2\times10^{18}


Option: 2

8.2\times10^{14}


Option: 3

8.2\times10^{16}


Option: 4

4.1\times10^{16}


Answers (1)

best_answer

As we have learnt,

Relationship between \Delta \mathrm{G}$ or $\Delta \mathrm{G}^{\circ}$ with $\mathrm{E}$ or $\mathrm{E}^{\circ}

Free energy change (\Delta \mathrm{G}) in an electrochemical cell can be related to electrical work done (E) in cell as follows 

\Delta \mathrm{G}=-\mathrm{nFE}

when we use standard conditions than 

\Delta \mathrm{G}^{\circ}=-n \mathrm{FE}^0

Here (\mathrm{E^o})= standard E.M.F of the cell

n = No. of moles of e- transferred 

F = Faraday's constant

So,

Here n is 2 because 2 electrons have been exchanged.

\Delta G^{\circ}=-2\times 96500\times 0.5 

\Delta G^{\circ}=-96500\; J/mol

Also \mathrm{\Delta G^{\circ}=-RT\; ln\left ( Kc \right )}

\mathrm{\Rightarrow K_c=antilog\left [ \frac{-\Delta G^{\circ}}{RT} \right ]}

Putting values we get,

\mathrm{K_c=8.2\times10^{16}}

Hence, Option number (3) is correct.

Posted by

sudhir.kumar

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