JEE Mains · Chemistry · STD 12 - 2. Electrochemistry
Consider the following electrochemical cell at standard condition.
\(\begin{aligned}
& \mathrm{Au}(\mathrm{s})\left|\mathrm{QH}_2, \mathrm{Q}\right| \mathrm{NH}_4 \mathrm{X}(0.01 \mathrm{M})| | \mathrm{Ag}^{+}(1 \mathrm{M}) \mid \mathrm{Ag}(\mathrm{s}) \\
& \mathrm{E}_{\text {cell }}=+0.4 \mathrm{~V}
\end{aligned}\)
The couple \(\mathrm{QH}_2 / \mathrm{Q}\) represents quinhydrone electrode, the half cell reaction is given below
The \(\mathrm{pK}_{\mathrm{b}}\) value of the ammonium halide salt \(\left(\mathrm{NH}_4 \mathrm{X}\right)\) used here is _________. (nearest integer)
- A 2
- B 4
- C 6
- D 8
Answer & Solution
Correct Answer
(C) 6
Step-by-step Solution
Detailed explanation
\begin{aligned} & \mathrm{QH}_2+2 \mathrm{Ag}^{+} \rightarrow 2 \mathrm{Ag}+\mathrm{Q}+2 \mathrm{H}^{+} \\ & \mathrm{E}=\mathrm{E}^{\circ}-\frac{0.06}{2} \log \left[\mathrm{H}^{+}\right]^2 \\ & \mathrm{E}=\mathrm{E}^{\circ}-0.06 \times \log \left[\mathrm{H}^{+}\right] \\ &…
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