Question

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

Answer 1

Answer: (A)

SRP : $ E _{ Zn ^{2+} / Zn }^{\circ}< E _{ Fe ^{2+} / Fe }^{\circ}< E _{ Cu ^{2+} / Cu }^{\circ}< E _{ Ag ^{+} / Ag }^{\circ}$
Reactivity order : $Zn > Fe > Cu > Ag$
In case of displacement reaction, more reactive metals (lower SRP) can displace less reactive metals (higher SRP) from their salt solution.
$CuSO _{4(\text { aq. })}+2 Ag _{( s )} \rightarrow Cu _{( s )}+ Ag _{2} SO _{4(\text { aq. })}$
Option (3)
Reaction is not possible
as $Ag$ is less reactive metal compare to $Cu$.