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Saturday, 31 October

JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 4 August 2021, Shift 2, Chemistry Q58

Question 58 of 90 in this shift, Chemistry question 28 of 30, Section B.

The standard electrode potentials of the reactions are given below. MnO4−+8H++5e−⇌Mn2++4H2O\mathrm{MnO_4^-} + 8\mathrm{H^+} + 5\mathrm{e^-} \rightleftharpoons \mathrm{Mn^{2+}} + 4\mathrm{H_2O} E∘=1.51 V\mathrm{E^\circ} = 1.51\ \mathrm{V} 2CO2+2H++2e−⇌H2C2O42\mathrm{CO_2} + 2\mathrm{H^+} + 2\mathrm{e^-} \rightleftharpoons \mathrm{H_2C_2O_4} E∘=−0.49 V\mathrm{E^\circ} = -0.49\ \mathrm{V} The equilibrium constant for the reaction 2MnO4−+6H++5H2C2O4⇌2Mn2++8H2O+10CO22\mathrm{MnO_4^-} + 6\mathrm{H^+} + 5\mathrm{H_2C_2O_4} \rightleftharpoons 2\mathrm{Mn^{2+}} + 8\mathrm{H_2O} + 10\mathrm{CO_2} is 10x10^x. The value of xx is ________ . (Nearest integer) [Given : 2.303 RTF\frac{2.303\,\mathrm{RT}}{\mathrm{F}} = 0.059 V]

Official answer

339

NTA final key.

Chapter
Electrochemistry
Topic
Nernst Equation
Idea tested
E°cell and Equilibrium

Same idea in other shifts

Asked 4× in all
  1. 1 Feb 2024, Shift 2 · Q85Consider the following redox reaction : MnO4−+H++H2C2O4⇌Mn2++H2O+CO2\mathrm{MnO_4^- + H^+ + H_2C_2O_4 \rightleftharpoons Mn^{2+} + H_2O + CO_2} The standard…MediumNumerical value
  2. 3 Aug 2021, Shift 1 · Q56The logarithm of equilibrium constant (log⁡10\log_{10}K) for the reaction…MediumNumerical value
  3. 8 Jan 2020, Shift 2 · Q48For an electrochemical cell Sn(s)∣Sn2+(aq, 1M)∣∣Pb2+(aq, 1M)∣Pb(s)\mathrm{Sn(s)|Sn^{2+}(aq,\ 1M)||Pb^{2+}(aq,\ 1M)|Pb(s)} the ratio…MediumNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.