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Electrochemistry question

2003 · Shift 0 · Q36
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Electrochemistry question

2003 · Shift 0 · Q36

JEE MainChemistryElectrochemistryMCQ+4 / −1
For the redox reaction ZnZnZn(s) + Cu2+Cu^{2+}Cu2+(0.1 M) →\to→ Zn2+Zn^{2+}Zn2+(1M) + CuCuCu(s) taking place in a cell, EcelloE_{cell}^oEcello​ is 1.10 volt. Ecell for the cell will be (2.303RTF2.303{{RT} \over F}2.303FRT​ = 0.0591)
  1. A
    1.80 volt
  2. B
    1.07 volt
  3. C
    0.82 volt
  4. D
    2.14 volt
View written solutionFree

Correct answer: B

  1. Write the cell reaction and identify electrons transferred

The reaction is Zn(s)+Cu2+(0.1 M)→Zn2+(1 M)+Cu(s)Zn(s) + Cu^{2+}(0.1\,M) \to Zn^{2+}(1\,M) + Cu(s)Zn(s)+Cu2+(0.1M)→Zn2+(1M)+Cu(s)

For this reaction:

  • Zn→Zn2++2e−Zn \to Zn^{2+} + 2e^-Zn→Zn2++2e−
  • Cu2++2e−→CuCu^{2+} + 2e^- \to CuCu2++2e−→Cu

So, the number of electrons transferred is n=2n=2n=2

  1. Use the Nernst equation

At 298 K298\,K298K, Ecell=Ecello−0.0591nlog⁡QE_{cell}=E_{cell}^o-\frac{0.0591}{n}\log QEcell​=Ecello​−n0.0591​logQ

Given: Ecello=1.10 VE_{cell}^o=1.10\,VEcello​=1.10V

  1. Calculate the reaction quotient QQQ

For the reaction Zn(s)+Cu2+(aq)→Zn2+(aq)+Cu(s)Zn(s)+Cu^{2+}(aq)\to Zn^{2+}(aq)+Cu(s)Zn(s)+Cu2+(aq)→Zn2+(aq)+Cu(s)

Solids are not included in QQQ, so Q=[Zn2+][Cu2+]Q=\frac{[Zn^{2+}]}{[Cu^{2+}]}Q=[Cu2+][Zn2+]​

Given concentrations: [Zn2+]=1 M,[Cu2+]=0.1 M[Zn^{2+}]=1\,M, \qquad [Cu^{2+}]=0.1\,M[Zn2+]=1M,[Cu2+]=0.1M

Hence, Q=10.1=10Q=\frac{1}{0.1}=10Q=0.11​=10

  1. Substitute into the Nernst equation

Since log⁡10=1\log 10 = 1log10=1, Ecell=1.10−0.05912(1)E_{cell}=1.10-\frac{0.0591}{2}(1)Ecell​=1.10−20.0591​(1)

Ecell=1.10−0.02955E_{cell}=1.10-0.02955Ecell​=1.10−0.02955

Ecell=1.07045 VE_{cell}=1.07045\,VEcell​=1.07045V

Thus, Ecell≈1.07 VE_{cell}\approx 1.07\,VEcell​≈1.07V

  1. Check options
  • A: 1.80 V1.80\,V1.80V ❌
  • B: 1.07 V1.07\,V1.07V ✅
  • C: 0.82 V0.82\,V0.82V ❌
  • D: 2.14 V2.14\,V2.14V ❌

Therefore, the correct option is B.

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