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Saturday, 31 October

JEE Main 2021 · ChemistryMultiple choiceDiagram basedMediumData or graph

JEE Main 17 March 2021, Shift 1, Chemistry Q34

Question 34 of 90 in this shift, Chemistry question 4 of 30, Section A.

The point of intersection and sudden increase in the slope, in the diagram given below, respectively, indicates :

The figure, in words

Ellingham-type diagram. Y-axis labelled "\Delta G^0 /kJ mol^-1 of O2" with ticks 0, -100, -200, ... -1200; x-axis "Temperature" with ticks 0 C/273 K, 400 C/673 K, 800 C/1073 K, 1200 C/1473 K, 1600 C/1873 K, 2000 C/2273 K. Straight (some kinked) lines labelled 4Cu + O2 -> 2Cu2O, 2Fe + O2 -> 2FeO, C + O2 -> CO2 (horizontal), 2CO + O2 -> 2CO2, 2C + O2 -> 2CO (downward sloping), 2Zn + O2 -> 2ZnO (kink near 800-1000 C), 4/3Al + O2 -> 2/3Al2O3, 2Mg + O2 -> 2MgO (kink near 1000-1100 C). A point labelled A (dot) where the Al and Mg lines intersect, near 1300-1400 C at about -800.
  1. (1)ΔG<0\Delta G < 0 and decomposition of the metal oxide
  2. (2)ΔG>0\Delta G > 0 and decomposition of the metal oxide
  3. (3)ΔG=0\Delta G = 0 and melting or boiling point of the metal oxideOfficial answer
  4. (4)ΔG=0\Delta G = 0 and reduction of the metal oxide

Official answer

Option 3

NTA final key.

Chapter
General Principles and Processes of Isolation of Elements
Topic
Gibbs Free Energy
Idea tested
Ellingham Diagram Phase Changes

Same topic in other shifts

All Gibbs Free Energy questions
  1. 2 Apr 2026, Shift 1 · Q75At the transition temperature TT, A⇌B\mathrm{A\rightleftharpoons B} and ΔG0=105−35log⁡T\Delta G^0=105-35\log T where A and B are two states of…MediumNumerical value
  2. 2 Apr 2026, Shift 2 · Q73Consider the following two half-cell reactions along with the standard reduction potential given:…HardNumerical value
  3. 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
  4. 5 Apr 2026, Shift 2 · Q54Consider the following data for the reaction X2(g)+Y2(g)⇌2XY(g)\mathrm{X_2(g)+Y_2(g)\rightleftharpoons 2XY(g)} at 600 K. The ΔrG⊖\Delta_r G^\ominus (in kJ…MediumSingle correct
  5. 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
  6. 2 Apr 2025, Shift 2 · Q54Which of the following graphs correctly represents the variation of thermodynamic properties of Haber's process ?HardDiagram basedHas a figure

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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.