NEET 2022 — Chemistry solution

NEET2022Chemistry

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 can not occur ?

A
CuSO $_{4}$ (aq) + Fe(s) $\to$ FeSO $_{4}$ (aq) + Cu(s)
B
FeSO $_{4}$ (aq) + Zn(s) $\to$ ZnSO $_{4}$ (aq) + Fe(s)
C
2CuSO $_{4}$ (aq) + 2Ag(s) $\to$ 2Cu(s) + Ag $_{2}$ SO $_{4}$ (aq)
D
CuSO $_{4}$ (aq) + Zn(s) $\to$ ZnSO $_{4}$ (aq) + Cu(s)

Solution

From the standard reduction potentials, the activity (reducing power) order of the metals is Zn $>$ Fe $>$ Cu $>$ Ag.

A displacement reaction proceeds only when a more reactive metal displaces a less reactive one from its salt.

Option (3) asks silver to displace copper from CuSO $_{4}$ , but silver is less reactive than copper, so this reaction cannot occur.

The other three reactions are feasible (Fe displaces Cu, Zn displaces Fe, and Zn displaces Cu).

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