Question

$E^{\circ }$ values of three metals are listed below.
$Z{n}_{\left(aq\right)}^{2+}+2e^{-}\to Z{n}_{\left(s\right)};E^{\circ }=-0.76V$
$F{e}_{\left(aq\right)}^{2+}+2e^{-}\to 2F{e}_{\left(s\right)};E^{\circ }=-0.44V$
$S{n}_{\left(aq\right)}^{2+}+2e^{-}\to S{n}_{\left(s\right)};E^{\circ }=-0.14V$
Which of the following statements are correct on the basis of the above information?
(i) Zinc will be corroded in preference to iron if zinc coating is broken on the surface.
(ii) If iron is coated with tin and the coating is broken on the surface then iron will be corroded.
(iii) Zinc is more reactive than iron but tin is less reactive than iron.

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

Answer 1

Answer: (C)

Iron coated with zinc does not get rusted even if cracks appear on the surface because $Zn$ will take part in redox reaction not $Fe$ as $Zn$ is more reactive than $Fe$. If iron is coated with tin and cracks appear on the surface, $Fe$ will take part in redox reaction because $Sn$ is less reactive than $Fe$.