Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Electrochemistry question

2021 · 27 Jul · Shift 2 · Q22
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Chemistry
  4. /Electrochemistry
  5. /2021 · 27 Jul · Shift 2 · Q22

Electrochemistry question

2021 · 27 Jul · Shift 2 · Q22

JEE MainChemistryElectrochemistryNumerical+4 / −1
For the cell Cu(s) | Cu2+Cu^{2+}Cu2+ (aq) (0.1 M) || Ag+Ag^+Ag+(aq) (0.01 M) | Ag(s) the cell potential E1 = 0.3095 V For the cell Cu(s) | Cu2+Cu^{2+}Cu2+ (aq) (0.01 M) || Ag+Ag^+Ag+(aq) (0.001 M) | Ag(s) the cell potential = ‾×\underline{\hspace{2cm}}\times​× 10 −-− 2 V. (Round off the nearest integer). [Use : 2.303RTF{{2.303RT} \over F}F2.303RT​ = 0.059]
Numerical answer
View written solutionFree

Correct answer: 28

  1. Write the cell reaction

For the cell Cu(s) ∣ Cu2+(aq) ∣∣ Ag+(aq) ∣ Ag(s)\text{Cu}(s)\,|\,\text{Cu}^{2+}(aq)\,||\,\text{Ag}^+(aq)\,|\,\text{Ag}(s)Cu(s)∣Cu2+(aq)∣∣Ag+(aq)∣Ag(s)

Half-reactions are:

  • Anode: Cu(s)→Cu2++2e−\text{Cu}(s) \rightarrow \text{Cu}^{2+} + 2e^-Cu(s)→Cu2++2e−
  • Cathode: Ag++e−→Ag(s)\text{Ag}^+ + e^- \rightarrow \text{Ag}(s)Ag++e−→Ag(s)

Multiplying the silver half-reaction by 2: 2Ag++2e−→2Ag(s)2\text{Ag}^+ + 2e^- \rightarrow 2\text{Ag}(s)2Ag++2e−→2Ag(s)

Overall reaction: Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s)\text{Cu}(s) + 2\text{Ag}^+ (aq) \rightarrow \text{Cu}^{2+}(aq) + 2\text{Ag}(s)Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s)

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


  1. Reaction quotient

For the reaction Cu(s)+2Ag+→Cu2++2Ag(s)\text{Cu}(s) + 2\text{Ag}^+ \rightarrow \text{Cu}^{2+} + 2\text{Ag}(s)Cu(s)+2Ag+→Cu2++2Ag(s)

the reaction quotient is Q=[Cu2+][Ag+]2Q=\frac{[\text{Cu}^{2+}]}{[\text{Ag}^+]^2}Q=[Ag+]2[Cu2+]​


  1. Use Nernst equation

At the same temperature, E=E∘−0.059nlog⁡QE = E^\circ - \frac{0.059}{n}\log QE=E∘−n0.059​logQ

Thus, E=E∘−0.0592log⁡([Cu2+][Ag+]2)E = E^\circ - \frac{0.059}{2}\log \left(\frac{[\text{Cu}^{2+}]}{[\text{Ag}^+]^2}\right)E=E∘−20.059​log([Ag+]2[Cu2+]​)


  1. For the first cell

Given: [Cu2+]=0.1,[Ag+]=0.01[\text{Cu}^{2+}] = 0.1, \quad [\text{Ag}^+] = 0.01[Cu2+]=0.1,[Ag+]=0.01

So, Q1=0.1(0.01)2=10−110−4=103Q_1 = \frac{0.1}{(0.01)^2} = \frac{10^{-1}}{10^{-4}} = 10^3Q1​=(0.01)20.1​=10−410−1​=103

Hence, E1=E∘−0.0592log⁡(103)E_1 = E^\circ - \frac{0.059}{2}\log(10^3)E1​=E∘−20.059​log(103) E1=E∘−0.0592×3E_1 = E^\circ - \frac{0.059}{2}\times 3E1​=E∘−20.059​×3 E1=E∘−0.0885E_1 = E^\circ - 0.0885E1​=E∘−0.0885

Given: E1=0.3095 VE_1 = 0.3095\,\text{V}E1​=0.3095V

Therefore, E∘=0.3095+0.0885=0.3980 VE^\circ = 0.3095 + 0.0885 = 0.3980\,\text{V}E∘=0.3095+0.0885=0.3980V


  1. For the second cell

Given: [Cu2+]=0.01,[Ag+]=0.001[\text{Cu}^{2+}] = 0.01, \quad [\text{Ag}^+] = 0.001[Cu2+]=0.01,[Ag+]=0.001

So, Q2=0.01(0.001)2=10−210−6=104Q_2 = \frac{0.01}{(0.001)^2} = \frac{10^{-2}}{10^{-6}} = 10^4Q2​=(0.001)20.01​=10−610−2​=104

Now, E2=E∘−0.0592log⁡(104)E_2 = E^\circ - \frac{0.059}{2}\log(10^4)E2​=E∘−20.059​log(104) E2=0.3980−0.0592×4E_2 = 0.3980 - \frac{0.059}{2}\times 4E2​=0.3980−20.059​×4 E2=0.3980−0.1180E_2 = 0.3980 - 0.1180E2​=0.3980−0.1180 E2=0.2800 VE_2 = 0.2800\,\text{V}E2​=0.2800V


  1. Convert to required form

We need: E2=‾×10−2 VE_2 = \underline{\hspace{1cm}} \times 10^{-2}\,\text{V}E2​=​×10−2V

Since 0.2800 V=28×10−2 V0.2800\,\text{V} = 28 \times 10^{-2}\,\text{V}0.2800V=28×10−2V

So the required integer is 28\boxed{28}28​


  1. Comparison with stored answer

Stored correct answer = 28

Our derived answer = 28

Hence, the answer agrees with the stored answer.

PreviousNext

More from Electrochemistry

  • Consider the following cell reaction : Cd(s)​+Hg2​SO4(s)​+59​H2​O(l)​⇌ CdSO4​.59​H2​O(s)​+2Hg(l)​ The value of Ecell0​ is 4.315 V at 25 ∘ C. If Δ H…2021 · Numerical
  • Match List - I with List - II Choose the most appropriate answer from the options given below : Includes table2021 · MCQ
  • The Gibbs change (in J) for the given reaction at [Cu2+] = [Sn2+] = 1 M and 298K is : Cu(s) + Sn2+(aq.) → Cu2+(aq.) + Sn(s); (ESn2+∣Sn0​=−0.16V, ECu2+∣Cu0​=0.34V) Take F = 96500…2020 · Numerical
  • For the disproportionation reaction 2Cu+(aq) ⇌ Cu(s) + Cu2+(aq) at 298 K. ln K (where K is the equilibrium constant) is ​ × 10–1. Given : (ECu2+/Cu+0​=0.16VECu+/Cu0​=0.52VFRT​=0.025…2020 · Numerical
  • Let CNaCl and CBaSO4​ be the conductances (in S) measured for saturated aqueous solutions of NaCl and BaSO4​, respectively, at a temperature T. Which of the following is false?2020 · MCQ
  • The photoelectric current from Na (Work function, w0 = 2.3 eV) is stopped by the output voltage of the cell Pt(s) | H2​ (g, 1 Bar) | HCl (aq., pH =1) | AgCl(s) | Ag(s). The pH of aq. HCl required to stop the photoelectric current…2020 · Numerical
  • An acidic solution of dichromate is electrolyzed for 8 minutes using 2A current. As per the following equation Cr2​O72−​ + 14H+ + 6e– → 2Cr3+ + 7H2​O The amount of Cr3+ obtained was 0.104 g. The efficiency of the…2020 · Numerical
  • ECu2+∣Cu0​= +0.34 V EZn2+∣Zn0​ = -0.76 V Identify the incorrect statement from the option below for the above cell : Includes diagram2020 · MCQ