JEE Main 2022 · 24 Jun · Shift 1 · Chemistry Q84

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ChemistryInteger+4 / -1Question 84 of 90

The cell potential for the following cell
$\mathrm{Pt\,|H_2(g)|H^+(aq)\,||\,Cu^{2+}(0.01\ M)|Cu(s)}$
is 0.576 V at 298 K. The pH of the solution is ______. (Nearest integer)

(Given : $E^\circ_{\mathrm{Cu^{2+}/Cu}}=0.34$ V and $\dfrac{2.303RT}F=0.06$ V)

Your answer

Answer and worked solution

Official answer: 5

Cell reaction. $\mathrm{H_2+Cu^{2+}\rightarrow2H^++Cu}$ , $n=2$ , $E^\circ=0.34$ V.

Nernst.
$E=0.34-\frac{0.06}2\log\frac{[\mathrm{H^+}]^2}{[\mathrm{Cu^{2+}}]}=0.34-0.03(-2\,\mathrm{pH}+2)=0.28+0.06\,\mathrm{pH}.$

Solve. $0.576=0.28+0.06\,\mathrm{pH}$ gives pH $\approx4.93$ , nearest integer 5.

Answer: 5

Topics:Nernst equation pH and ionisation

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JEE Main 2022 · 24 Jun · Shift 1, Chemistry question 84