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Saturday, 31 October

JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 24 February 2021, Shift 2, Chemistry Q53

Question 53 of 90 in this shift, Chemistry question 23 of 30, Section B.

Assuming ideal behaviour, the magnitude of log K for the following reaction at 25∘25^\circC is x×10−1x \times 10^{-1}. The value of xx is __________. (Integer answer) 3HC≡CH(g)⇌C6H6(l)\mathrm{3HC{\equiv}CH_{(g)} \rightleftharpoons C_6H_{6(l)}} [Given : ΔfG∘(HC≡CH)=−2.04×105 J mol−1\Delta_fG^\circ(\mathrm{HC{\equiv}CH}) = -2.04 \times 10^5\ \mathrm{J\ mol^{-1}} ; ΔfG∘(C6H6)=−1.24×105 J mol−1\Delta_fG^\circ(\mathrm{C_6H_6}) = -1.24 \times 10^5\ \mathrm{J\ mol^{-1}} ; R =8.314 J K−1 mol−1= 8.314\ \mathrm{J\ K^{-1}\ mol^{-1}}]

Official answer

855

NTA final key.

Chapter
Equilibrium
Topic
Gibbs Free Energy
Idea tested
Gibbs Energy and Equil

Same idea in other shifts

Asked 10× in all
  1. 4 Apr 2026, Shift 2 · Q72For the following reaction at 50 ∘^\circC and at 2 atm pressure, 2N2O5(g)⇌2N2O4(g)+O2(g)\mathrm{2N_2O_5(g)\rightleftharpoons2N_2O_4(g)+O_2(g)}…HardNumerical value
  2. 6 Apr 2026, Shift 1 · Q75Consider the reaction X⇌Y\mathrm{X\rightleftharpoons Y} at 300 K. If ΔHθ\Delta H^\theta and K are 28.40 kJ mol−1^{-1} and 1.8×10−71.8\times10^{-7}…MediumNumerical value
  3. 1 Feb 2024, Shift 2 · Q82For a certain reaction at 300K, K = 10, then ΔG∘\Delta G^\circ for the same reaction is −- ________ ×10−1\times 10^{-1} kJ mol−1^{-1}. (Given…EasyNumerical value
  4. 31 Jan 2024, Shift 1 · Q84Consider the following reaction at 298 K. 32O2(g)⇌O3(g)\frac{3}{2}\mathrm{O_{2(g)}} \rightleftharpoons \mathrm{O_{3(g)}}.…EasyNumerical value
  5. 6 Apr 2023, Shift 1 · Q84The value of log K for the reaction A⇌B\mathrm{A \rightleftharpoons B} at 298 K is ________. (Nearest integer) Given:…MediumNumerical value
  6. 24 Jun 2022, Shift 1 · Q822O3(g)⇌3O2(g)\mathrm{2O_3(g)\rightleftharpoons 3O_2(g)} At 300 K, ozone is fifty percent dissociated. The standard free energy change at this…MediumNumerical value
  7. 25 Jun 2022, Shift 1 · Q84The standard entropy change for the reaction 4Fe(s)+3O2(g)→2Fe2O3(s)4\mathrm{Fe(s)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{Fe_2O_3(s)} is…EasyNumerical value
  8. 26 Jun 2022, Shift 2 · Q8640% of HI undergoes decompostion to H2\mathrm{H_2} and I2\mathrm{I_2} at 300 K. ΔG⊖\Delta G^\ominus for this decompostion reaction at one…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.