Question

Is the following reaction possible or not? Explain with reasons. \[Zn(NO_3)_2 + 2Ag \rightarrow 2AgNO_3 + Zn\]

Hint:

Zn is above Ag in the activity series; Ag cannot displace Zn. Check \(E^{\circ}_{cell}\) is negative.

Answer 1

Step 1: What the reaction claims. It shows silver metal displacing zinc from zinc nitrate. For displacement, the free metal (Ag) must be more reactive than the metal in the salt (Zn).
Step 2: Compare reactivities. Zinc is far more reactive (more electropositive) than silver. Standard reduction potentials: \(Zn^{2+}/Zn = -0.76\,V\) and \(Ag^+/Ag = +0.80\,V\). Zinc sits above silver in the activity series.
Step 3: Test with cell potential. Here Ag would be oxidised (anode) and \(Zn^{2+}\) reduced (cathode):
\[E^{\circ}_{cell} = E^{\circ}_{cathode} - E^{\circ}_{anode} = (-0.76) - (+0.80) = -1.56\,V\]
A negative \(E^{\circ}_{cell}\) means \(\Delta G = -nFE^{\circ}_{cell} > 0\), so the reaction is non-spontaneous.
Step 4: Conclusion. Silver cannot displace zinc; the reaction is NOT possible. In fact the reverse, \(Zn + 2AgNO_3 \rightarrow Zn(NO_3)_2 + 2Ag\), is the feasible one.
\[\boxed{\text{Reaction not possible (}E^{\circ}_{cell} = -1.56\,V\text{)}}\]