Question

What is $ {{\text{G}}^{\text{o}}} $ at 298 K for the reaction, $ \text{2VO}_{2}^{+}(aq)+4{{H}^{+}}(aq)+Cd(s)\xrightarrow{{}}2V{{O}^{2+}}(aq) $ $ +2{{H}_{2}}O(l)+C{{d}^{2+}}(aq) $

• A. $ -271\,kJ $
• B. $ 1.403\,J $
• C. $ -\text{ }135\text{ }kJ $
• D. $ -\text{ }115\text{ }kJ $

Answer 1

Answer: (A)

$ 2{{e}^{-}}+2VO_{2}^{+}+4{{H}^{+}}\xrightarrow{{}}2V{{O}^{2+}}+2{{H}_{2}}O; $ $ *\,\,\Delta {{E}^{o}}=1.0\,V $ ?(i) $ Cd\xrightarrow{{}}C{{d}^{2+}}2{{e}^{-}}; $ $ ^{*}\Delta {{E}^{o}}=+\,0.40\,V $ ?(ii) On adding Eq (i) and (ii), we get $ 2VO_{2}^{+}+4{{H}^{+}}+Cd\to 2V{{O}^{2+}}+2{{H}_{2}}O+C{{d}^{2+}}; $ $ E_{cell}^{o}=1.0+0.40=1.40\,V $ $ \Delta {{G}^{o}}=-nFE_{cell}^{o}=-2\times 96500\times 1.4 $ $ =-270200\,J=-271\,kJ $ * Since in this $ \text{Q}\text{.}{{\text{E}}^{\text{o}}} $ values are not given, it is incorrect. These values are taken from reference books.