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  • At , the standard electrode potentials of <img alt="\mathrm{Cu}^{2+}/\mathrm{Cu} ,\mathrm{Zn}^{2+}/\mathrm{Zn}, \mathrm{Fe

At 298 \mathrm{~K}, the standard electrode potentials of \mathrm{Cu}^{2+}/\mathrm{Cu} ,\mathrm{Zn}^{2+}/\mathrm{Zn}, \mathrm{Fe}^{2+}/ \mathrm{Fe} and \mathrm{Ag}^{+} / \mathrm{Ag}$ are $0.34 \mathrm{~V}$, $-0.76 \mathrm{~V},-0.44 \mathrm{~V}$ and $0.80 \mathrm{~V}, respectively.
On the basis of standard electrode potential, predict which of the following reaction can not occur?

Option: 1

\mathrm{CuSO}_{4}(\mathrm{aq})+\mathrm{Fe}(\mathrm{s}) \rightarrow \mathrm{FeSO}_{4}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})


Option: 2

\mathrm{FeSO}_{4}(\mathrm{aq})+\mathrm{Zn}(\mathrm{s}) \rightarrow \mathrm{ZnSO}_{4}(\mathrm{aq})+\mathrm{Fe}(\mathrm{s})


Option: 3

2 \mathrm{CuSO}_{4}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s}) \rightarrow 2 \mathrm{Cu}(\mathrm{s})+\mathrm{Ag}_{2} \mathrm{SO}_{4}(\mathrm{aq})


Option: 4

\mathrm{CuSO}_{4}(\mathrm{aq})+\mathrm{Zn}\mathrm{(s)} \rightarrow \mathrm{ZnSO}_{4}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})


Answers (1)

best_answer

Given Standard electrical potentials so order will be

\begin{aligned} &\mathrm{E}_{\mathrm{Zn}^{2+} / \mathrm{Zn}}^{0}<\mathrm{E}^{0}_{\mathrm{Fe}^{2+} / \mathrm{Fe}}<\mathrm{E}^{0} _{\mathrm{Cu}^{2+} / \mathrm{Cu}}<\mathrm{E}^{0} _{\mathrm{Ag}^{2+} / \mathrm{Ag}}\\ \end{aligned}

-0.76             -0.44           0.34                0.80

From above data,

\mathrm{Ag^{2+}} can oxidise others then get reduced to

\mathrm{Zn^{2+}} cannot oxidise others

\mathrm{Fe^{2+}} can oxidise only \mathrm{Zn} and \mathrm{Fe} metals but not \mathrm{Cu} and \mathrm{Ag}

\mathrm{Cu^{2+}} can oxidise only \mathrm{Zn} and \mathrm{Fe} metals but it cannot oxidise \mathrm{Ag} metal due to high value

In reaction \begin{aligned} 2 \mathrm{CuSO}_{4}(\text { aq })+2 \mathrm{Ag}(s) \rightarrow & 2 \mathrm{Cu}_{4}(\mathrm{~s}) +\mathrm{Ag}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \end{aligned}

\mathrm{Cu^{2+}} is oxidising \mathrm{Ag} which is not possible, so this reaction can not occur.

hence correct option is 3.

Posted by

Pankaj Sanodiya

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