Question

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

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

Answer 1

Answer: (D)

$\ce{ Pb^{+2} , Sn^{+4} }$

Answer 2

${PbO_2 \to PbO}$ ${\Delta G_{298} < 0}$ 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.