Question

Which one of the following pairs of reactants can undergo a reaction under appropriate conditions ?

$i.{\mathrm{MgSO}}_4+\mathrm{Fe}\mathrm{ii}.{\mathrm{FeSO}}_4+\mathrm{Zn}\mathrm{iii}.{\mathrm{MgSO}}_4+\mathrm{Pb}\mathrm{iv}.{\mathrm{CuSO}}_4+\mathrm{Fe}$

[0.8 mark]

• A. (i) and (iii)
• B. (iii) and (iv)
• C. (i), (ii) and (iv)
• D. (ii) and (iv)

Answer 1

The correct option is D (ii) and (iv)

According to the reactivity series, Zn is more reactive than Fe, and Fe is more reactive than Cu. Reactivity of metals: Mg > Zn > Fe > Pb > Cu. As a result, only in these two cases, reactants can undergo displacement reaction under appropriate conditions.

${\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+\mathrm{Zn}\left(s\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Fe}\left(s\right)$
${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+\mathrm{Fe}\left(s\right)\to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(s\right)$
${\mathrm{MgSO}}_4\left(\mathrm{aq}\right)+\mathrm{Fe}\left(s\right)\to \mathrm{No}\mathrm{reaction}$
${\mathrm{MgSO}}_4\left(\mathrm{aq}\right)+\mathrm{Pb}\left(s\right)\to \mathrm{No}\mathrm{reaction}$