Electrochemistry Result Question 32
Passage
Tollen’s reagent is used for the detection of aldehydes. When a solution of $\mathrm{AgNO}_3$ is added to glucose with $\mathrm{NH}_4 \mathrm{OH}$, then gluconic acid is formed.
$ \begin{aligned} & \mathrm{Ag}^{+}+e^{-} \longrightarrow \mathrm{Ag} ; \quad E_{\text {red }}^{\circ}=0.80 \mathrm{~V} \\ & \mathrm{C}6 \mathrm{H}{12} \mathrm{O}_6+\mathrm{H}_2 \mathrm{O} \longrightarrow {\mathrm{C}6 \mathrm{H}{12} \mathrm{O}7}{\text { (Gluconic acid )}} +2 \mathrm{H}^{+}+2 e^{-} \text {; } \quad E{\text {oxi }}^{\circ}=-0.05 \mathrm{~V} \\ & \mathrm{Ag}\left(\mathrm{NH}_3\right)_2^{+}+e^{-} \longrightarrow \mathrm{Ag}(s)+2 \mathrm{NH}3 ; \quad E{\text {red }}^{\circ}=0.337 \mathrm{~V} \\ \end{aligned} $
[Use $2.303 \times \frac{R T}{F}=0.0592$ and $\frac{F}{R T}=38.92$ at 298 K ]
$ (2006,3 \times 4 M=12 \mathrm{M}) $
32. $2 \mathrm{Ag}^{+}+\mathrm{C}6 \mathrm{H}{12} \mathrm{O}_6+\mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{Ag}(s)+\mathrm{C}6 \mathrm{H}{12} \mathrm{O}_7+2 \mathrm{H}^{+}$
Find $\ln K$ of this reaction.
(a) 66.13
(b) 58.38
(c) 28.30
(d) 46.29
Show Answer
Answer:
Correct Answer: 32. ( b )
Solution:
$E^{\circ}$ for $2 \mathrm{Ag}^{+}+\mathrm{C}6 \mathrm{H}{12} \mathrm{O}_6+\mathrm{H}_2 \mathrm{O} \rightleftharpoons 2 \mathrm{Ag}(s)$ $ +\mathrm{C}6 \mathrm{H}{12} \mathrm{O}_7+2 \mathrm{H}^{+} \text {is } 0.75 \mathrm{~V} $
Also $\quad E^{\circ}=\frac{0.0592}{2} \log K \Rightarrow \log K=\frac{2 E^{\circ}}{0.0592}=25.33$
$ \Rightarrow \quad \ln K=2.303 \log K=58.35 $
BETA
