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The standard reduction potentials for  Zn2+/Zn, Ni2+ / Ni and Fe2+ / Fe are –0.76, –0.23 and –0.44 V respectively.

The reaction   X + Y2+ \rightarrow X2+ + Y will be spontaneous when :

Option: 1

X = Ni, Y = Fe


Option: 2

X = Ni, Y = Zn


Option: 3

X = Fe, Y = Zn


Option: 4

X = Zn, Y = Ni


Answers (1)

best_answer

For a spontaneous reaction, Eo must be positive.

So, Eo = Eo reduced constituent - Eoxidized  constituent

Eo =  (-0.23) - (-0.76)

[We get this by maximizing EoR and minimizing EoO]

Alternatively, we can also solve this qualitatively. Elements with a low value of SRP are good reducing agents and therefore, can be easily oxidized. Also, elements with a low negative value of SRP are good oxidizing agents and can be reduced easily. Keeping the above in mind, we can clearly see that \mathrm{X=Zn\:\: and\:\: Y=Ni}   and the reaction is:

\mathrm{Zn+Ni^{2+}\rightarrow Zn^{2+}+Ni} 

Therefore, option(4) is correct

Posted by

Ramraj Saini

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