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Electrochemistry question

2022 · 26 Jun · Shift 2 · Q21
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Electrochemistry question

2022 · 26 Jun · Shift 2 · Q21

JEE MainChemistryElectrochemistryNumerical+4 / −1
CuCuCu(s) + Sn2+Sn^{2+}Sn2+ (0.001M) →\to→ Cu2+Cu^{2+}Cu2+ (0.01M) + SnSnSn(s) The Gibbs free energy change for the above reaction at 298 K is x ×\times× 10 −-− 1 kJ mol −-− 1. The value of x is ‾\underline{\hspace{2cm}}​. [nearest integer] [Given : ECu2+/CuΘ=0.34 VE_{C{u^{2 + }}/Cu}^\Theta = 0.34\,VECu2+/CuΘ​=0.34V; ESn2+/SnΘ=−0.14 VE_{S{n^{2 + }}/Sn}^\Theta = - 0.14\,VESn2+/SnΘ​=−0.14V ; F = 96500 C mol −-− 1]
Numerical answer
View written solutionFree

Correct answer: 983

  1. Write the reaction and identify electron transfer

Given reaction: Cu(s)+Sn2+(0.001M)→Cu2+(0.01M)+Sn(s)Cu(s) + Sn^{2+}(0.001M) \rightarrow Cu^{2+}(0.01M) + Sn(s)Cu(s)+Sn2+(0.001M)→Cu2+(0.01M)+Sn(s)

Half-reactions are:

  • Oxidation: Cu(s)→Cu2++2e−Cu(s) \rightarrow Cu^{2+} + 2e^-Cu(s)→Cu2++2e−
  • Reduction: Sn2++2e−→Sn(s)Sn^{2+} + 2e^- \rightarrow Sn(s)Sn2++2e−→Sn(s)

So, number of electrons transferred: n=2n=2n=2


  1. Find standard cell potential

Given standard reduction potentials: ECu2+/Cu∘=0.34 VE^\circ_{Cu^{2+}/Cu}=0.34\,VECu2+/Cu∘​=0.34V ESn2+/Sn∘=−0.14 VE^\circ_{Sn^{2+}/Sn}=-0.14\,VESn2+/Sn∘​=−0.14V

In the given reaction:

  • Sn2+Sn^{2+}Sn2+ is reduced at cathode
  • CuCuCu is oxidized at anode

Therefore, Ecell∘=Ecathode∘−Eanode∘E^\circ_{cell}=E^\circ_{cathode}-E^\circ_{anode}Ecell∘​=Ecathode∘​−Eanode∘​ Ecell∘=(−0.14)−(0.34)=−0.48 VE^\circ_{cell}=(-0.14)-(0.34)=-0.48\,VEcell∘​=(−0.14)−(0.34)=−0.48V


  1. Calculate reaction quotient QQQ

For the reaction Cu(s)+Sn2+(aq)→Cu2+(aq)+Sn(s)Cu(s)+Sn^{2+}(aq)\rightarrow Cu^{2+}(aq)+Sn(s)Cu(s)+Sn2+(aq)→Cu2+(aq)+Sn(s)

Solids are omitted, so Q=[Cu2+][Sn2+]=0.010.001=10Q=\frac{[Cu^{2+}]}{[Sn^{2+}]}=\frac{0.01}{0.001}=10Q=[Sn2+][Cu2+]​=0.0010.01​=10


  1. Apply Nernst equation

At 298 K298\,K298K, E=E∘−0.0591nlog⁡QE=E^\circ-\frac{0.0591}{n}\log QE=E∘−n0.0591​logQ

So, E=−0.48−0.05912log⁡10E=-0.48-\frac{0.0591}{2}\log 10E=−0.48−20.0591​log10 E=−0.48−0.05912(1)E=-0.48-\frac{0.0591}{2}(1)E=−0.48−20.0591​(1) E=−0.48−0.02955=−0.50955 VE=-0.48-0.02955=-0.50955\,VE=−0.48−0.02955=−0.50955V


  1. Calculate Gibbs free energy change

Relation: ΔG=−nFE\Delta G=-nFEΔG=−nFE

Substitute values: ΔG=−2×96500×(−0.50955)\Delta G=-2\times 96500 \times (-0.50955)ΔG=−2×96500×(−0.50955) ΔG=98343.15 J mol−1\Delta G=98343.15\,J\,mol^{-1}ΔG=98343.15Jmol−1

Convert to kJ mol−1^{-1}−1: ΔG=98.343 kJ mol−1\Delta G=98.343\,kJ\,mol^{-1}ΔG=98.343kJmol−1


  1. Match with the form given

Given: ΔG=x×10−1 kJ mol−1\Delta G = x\times 10^{-1}\,kJ\,mol^{-1}ΔG=x×10−1kJmol−1

That means x×10−1=98.343x\times 10^{-1}=98.343x×10−1=98.343 x=983.43x=983.43x=983.43

Nearest integer: x=983x=983x=983


  1. Final Answer

983\boxed{983}983​

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