Question

Based on the reactions given below, which is the correct decreasing order of the reactivity of the metals?

• A. $\mathrm{Cu}>\mathrm{Ag}>\mathrm{Fe}>\mathrm{Zn}$
• B. $\mathrm{Fe}>\mathrm{Zn}>\mathrm{Cu}>\mathrm{Ag}$
• C. $\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}$
• D. $\mathrm{Ag}>\mathrm{Cu}>\mathrm{Zn}>\mathrm{Fe}$

Answer 1

The correct option is C

$\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}$

The explanation for the correct option

(C) $\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}$

1. Reactivity of a metal refers to the ability of that metal to replace another metal (less reactive metal) from a compound.

Explanation of the given reactions

(i) $\mathrm{Zn}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

Zinc $\left(\mathrm{Zn}\right)$ being more reactive than copper $\left(\mathrm{Cu}\right)$ replaces copper from copper sulfate $\left({\mathrm{CuSO}}_4\right)$ to form zinc sulfate $\left({\mathrm{ZnSO}}_4\right)$.

(ii)$\mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)$

Copper being more reactive than silver $\left(\mathrm{Ag}\right)$ replaces silver from silver nitrate $\left({\mathrm{AgNO}}_3\right)$ to form copper nitrate $\left(\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\right)$.

(iii)$\mathrm{Zn}\left(\mathrm{s}\right)+{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Fe}\left(\mathrm{s}\right)$

Zinc being more reactive than iron $\left(\mathrm{Fe}\right)$ replaces iron from ferrous sulfate $\left({\mathrm{FeSO}}_4\right)$ to form zinc sulfate $\left({\mathrm{ZnSO}}_4\right)$.

(iv)$\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

Iron being more reactive than copper replaces copper from copper sulfate $\left({\mathrm{CuSO}}_4\right)$ to form ferrous sulfate $\left({\mathrm{FeSO}}_4\right)$.

So, from the above reactions the reactivity of the metals is in the order: $\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}>\mathrm{Ag}$.

Therefore, the correct option is (C).