Q. Consider the following reaction : $2{Ag}^{+}C_{6}H_{12}O_{6} + H_{2}O\ \rightarrow 2Ag(s) + C_{6}H_{12}O_{7} + 2H^{+}$ When ammonia is added to the solution, pH is raised to 11. Which half-cell reaction is affected by pH and by how much? ${Ag}^{+} + e^{-}\ \rightarrow Ag;\ \ E_{red}^{{^\circ}} = 0.8\ V$ $C_{6}H_{12}O_{6} + H_{2}O\ \rightarrow C_{6}H_{12}O_{7} + 2H^{+} + 2e^{-};\ E_{red}^{{^\circ}} = - 0.05\ V$ $Ag\left( {NH}_{3} \right)_{2}^{+} + \ e^{-}\ \rightarrow Ag(s) + {NH}_{3};\ \ E_{red}^{{^\circ}} = 0.337\ V$
A) $E_{oxid.}^{{^\circ}}$ will increase by a factor of 0.65 from $E_{oxid.}^{{^\circ}}$
B) $E_{oxid.}^{{^\circ}}$ will decrease by a factor of 0.65 from $E_{oxid.}^{{^\circ}}$
C) $E_{red.}^{{^\circ}}$ will increase by a factor of 0.65 from $E_{red.}^{{^\circ}}$
D) $E_{red.}^{{^\circ}}$ will decrease by a factor of 0.65 from $E_{red.}^{{^\circ}}$
Explanation
(a)
As ammonia is added the concentration of $H^{+}$ decreases, thus oxidation potential increases by 0.65
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.