Question

$ PbO_2 \rightarrow PbO \, \Delta G_{298} < 0 $
$ SnO_2 \rightarrow SnO \, \Delta G_{298} > 0$
Most probable oxidation state of Pb & Sn will be :

• A. $ Pb^{+4} , Sn^{+2} $
• B. $Pb^{+4} , Sn^{+2} $
• C. $ Pb^{+2} , Sn^{+2} $
• D. $ Pb^{+2} , Sn^{+4} $

Answer 1

Answer: (D)

$PbO_2 \to PbO$
$\Delta G_{298} < 0$
For this reaction $\Delta G$ is negative, hence $Pb^{2+}$ is more stable than $Pb^{4+}$.
$SnO_2 \to SnO \Delta G_{298} >0$
For this reaction $\Delta G$ is positive,
hence $Sn^{4+}$ is more stable than $Sn^{2+}$.
because for spontaneous change $\Delta G$ must be negative.