Question

The standard reduction potentials for two half-cell reactions are given below.
$C{d}^{2+}(aq)+2e^{-}\to Cd(s);E^{\circ }=-0.40V$
$A{g}^{+}(aq)+e^{-}\to Ag(s),E^{\circ }=0.80V$
The standard free energy change for the reaction
$2A{g}^{+}(aq)+Cd(s)\to 2Ag(s)+C{d}^{2+}(aq)$ is given by

• A. $115.8kJ$
• B. $-115.8kJ$
• C. $-231.6kJ$
• D. $231.6kJ$

Answer 1

Answer: (C)

$2A{g}^{+}(aq)+2e^{-}\to 2Ag(s);E^{\circ }=0.80V$
$Cd(s)\to C{d}^{2+}(aq)+2e^{-};E^{\circ }=0.40V$
$2A{g}^{+}(aq)+Cd(s)\to 2Ag(s)+C{d}^{2+}(aq);E^{\circ }=1.20V$
$\Delta G=-nF{E}^{\circ }=-2\times 96500\times 1.20=-231.6kJ$