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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumConceptual

JEE Main 17 March 2021, Shift 1, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

Two ideal polyatomic gases at temperatures T1T_1 and T2T_2 are mixed so that there is no loss of energy. If F1F_1 and F2F_2, m1m_1 and m2m_2, n1n_1 and n2n_2 be the degrees of freedom, masses, number of molecules of the first and second gas respectively, the temperature of mixture of these two gases is :
  1. (1)n1F1T1+n2F2T2n1+n2\frac{n_1F_1T_1+n_2F_2T_2}{n_1+n_2}
  2. (2)n1F1T1+n2F2T2F1+F2\frac{n_1F_1T_1+n_2F_2T_2}{F_1+F_2}
  3. (3)n1F1T1+n2F2T2n1F1+n2F2\frac{n_1F_1T_1+n_2F_2T_2}{n_1F_1+n_2F_2}Official answer
  4. (4)n1T1+n2T2n1+n2\frac{n_1T_1+n_2T_2}{n_1+n_2}

Official answer

Option 3

NTA final key.

Chapter
Kinetic Theory
Topic
Kinetic Theory of Gases
Idea tested
Internal Energy of Gas Mixtures

Same idea in other shifts

Asked 7× in all
  1. 1 Feb 2024, Shift 1 · Q39Two moles a monoatomic gas is mixed with six moles of a diatomic gas. The molar specific heat of the mixture at constant volume is :EasySingle correct
  2. 31 Jan 2024, Shift 2 · Q39A gas mixture consists of 8 moles of argon and 6 moles of oxygen at temperature T. Neglecting all vibrational modes, the total internal…EasySingle correct
  3. 10 Apr 2023, Shift 2 · Q33A gas mixture consists of 2 moles of oxygen and 4 moles of neon at temperature T. Neglecting all vibrational modes, the total internal…EasySingle correct
  4. 29 Jul 2022, Shift 1 · Q54One mole of a monoatomic gas is mixed with three moles of a diatomic gas. The molecular specific heat of mixture at constant volume is…MediumNumerical value
  5. 2 Sep 2020, Shift 1 · Q9A gas mixture consists of 3 moles of oxygen and 5 moles of argon at temperature TT. Assuming the gases to be ideal and the oxygen bond to…EasySingle correct
  6. 4 Sep 2020, Shift 1 · Q23A closed vessel contains 0.1 mole of a monatomic ideal gas at 200 K. If 0.05 mole of the same gas at 400 K is added to it, the final…EasyNumerical 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.