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Electrochemistry question

2024 · 1 Feb · Shift 1 · Q23
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Electrochemistry question

2024 · 1 Feb · Shift 1 · Q23

JEE MainChemistryElectrochemistryNumerical+4 / −1
The potential for the given half cell at 298 K298 \mathrm{~K}298 K is (-) ‾\underline{\hspace{2cm}}​×10−2 V\times 10^{-2} \mathrm{~V}×10−2 V 2H(aq)++2e−⟶H2( g)[H+]=1M,PH2=2 atm\begin{aligned} & 2 \mathrm{H}_{(\mathrm{aq})}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{H}_2(\mathrm{~g}) \\\\ & {\left[\mathrm{H}^{+}\right]=1 \mathrm{M}, \mathrm{P}_{\mathrm{H}_2}=2 \mathrm{~atm}} \end{aligned}​2H(aq)+​+2e−⟶H2​( g)[H+]=1M,PH2​​=2 atm​(Given : 2.303RT/F=0.06 V,log⁡2=0.32.303 \mathrm{RT} / \mathrm{F}=0.06 \mathrm{~V}, \log 2=0.32.303RT/F=0.06 V,log2=0.3 )
Numerical answer
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Correct answer: 1

  1. Write the half-reaction and standard potential

    The given half-cell is: 2H(aq)++2e−→H2(g)2H^+_{(aq)} + 2e^- \rightarrow H_2(g)2H(aq)+​+2e−→H2​(g)

    This is the standard hydrogen electrode, so E∘=0E^\circ = 0E∘=0

  2. Apply the Nernst equation

    For the reduction reaction, E=E∘−0.06nlog⁡QE = E^\circ - \frac{0.06}{n}\log QE=E∘−n0.06​logQ at 298 K298\,\text{K}298K.

    Here, n=2n=2n=2.

  3. Write the reaction quotient

    For 2H++2e−→H22H^+ + 2e^- \rightarrow H_22H++2e−→H2​ the reaction quotient is Q=PH2[H+]2Q = \frac{P_{H_2}}{[H^+]^2}Q=[H+]2PH2​​​

    Given: [H+]=1 M,PH2=2 atm[H^+] = 1\,\text{M}, \quad P_{H_2}=2\,\text{atm}[H+]=1M,PH2​​=2atm

    So, Q=2(1)2=2Q = \frac{2}{(1)^2} = 2Q=(1)22​=2

  4. Substitute into Nernst equation

    E=0−0.062log⁡2E = 0 - \frac{0.06}{2}\log 2E=0−20.06​log2

    Using log⁡2=0.3\log 2 = 0.3log2=0.3, E=−0.03×0.3E = -0.03 \times 0.3E=−0.03×0.3 E=−0.009 VE = -0.009\,\text{V}E=−0.009V

  5. Express in the required form

    We need: (−)  ‾×10−2 V(-)\;\underline{\hspace{2cm}} \times 10^{-2}\,\text{V}(−)​×10−2V

    Since −0.009 V=−0.9×10−2 V-0.009\,\text{V} = -0.9 \times 10^{-2}\,\text{V}−0.009V=−0.9×10−2V

    The integer to be filled is: 1\boxed{1}1​ (taking the nearest integer)

  6. Comparison with stored answer

    Derived answer = 111

    Stored correct answer = 111

    Hence, they agree.

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