Solved: CHEMISTRY Question for NEET

neet CHEMISTRYMedium

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

$CuSO_4(aq) + Zn(s) \rightarrow ZnSO_4(aq) + Cu(s)$

$CuSO_4(aq) + Fe(s) \rightarrow FeSO_4(aq) + Cu(s)$

$FeSO_4(aq) + Zn(s) \rightarrow ZnSO_4(aq) + Fe(s)$

$2CuSO_4(aq) + 2Ag(s) \rightarrow 2Cu(s) + Ag_2SO_4(aq)$

Step-by-Step Solution

For a reaction to be spontaneous, $E^{\circ}_{cell}$ must be positive. For $2CuSO_4(aq) + 2Ag(s) \rightarrow 2Cu(s) + Ag_2SO_4(aq)$ , $E^{\circ}_{cell} = E^{\circ}_{cathode} - E^{\circ}_{anode} = 0.34 V - 0.80 V = -0.46 V$ . Since $E^{\circ}_{cell}$ is negative, the reaction cannot occur.

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