Electrochemistry Result Question 34
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}) $
34. Ammonia is always added in this reaction. Which of the following must be incorrect?
(a) $\mathrm{NH}_3$ combines with $\mathrm{Ag}^{+}$to form a complex
(b) $\mathrm{Ag}\left(\mathrm{NH}_3\right)_2^{+}$is a stronger oxidising reagent than $\mathrm{Ag}^{+}$
(c) In the absence of $\mathrm{NH}_3$ silver salt of gluconic acid is formed
(d) $\mathrm{NH}_3$ has affected the standard reduction potential of glucose/gluconic acid electrode
Show Answer
Answer:
Correct Answer: 34. ( d )
Solution:
- $\mathrm{NH} _3$ has no effect on the $E^{\circ}$ of glucose/gluconic acid electrode.
BETA
