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JEE Main 20266 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
6 April
Shift
Evening Shift
Subject
Physics
Chapter
Kinetic Theory of Gases

JEE Main 2026 · 6 April · Evening Shift · Physics · Kinetic Theory of Gases

If 2 mole of an ideal monoatomic gas at temperature T , is mixed...

If 22 mole of an ideal monoatomic gas at temperature TT, is mixed with 66 mole of another ideal monoatomic gas at temperature 2T2T then the temperature of mixture is :

Options

  1. A52T\dfrac{5}{2}T
  2. B54T\dfrac{5}{4}T
  3. C72T\dfrac{7}{2}T
  4. D74T\dfrac{7}{4}T

Correct answer

D. 74T\dfrac{7}{4}T

Step-by-step solution

Using the principle of conservation of internal energy for the mixture of ideal gases:

Umix=U1+U2U_{mix} = U_1 + U_2

(n1+n2)CVTmix=n1CVT1+n2CVT2(n_1 + n_2) C_{V} T_{mix} = n_1 C_{V} T_1 + n_2 C_{V} T_2

Since both gases are monoatomic, their molar heat capacities at constant volume are equal (CV=32RC_{V} = \dfrac{3}{2}R).

(n1+n2)Tmix=n1T1+n2T2(n_1 + n_2) T_{mix} = n_1 T_1 + n_2 T_2

Substituting the given values n1=2n_1 = 2, T1=TT_1 = T, n2=6n_2 = 6, and T2=2TT_2 = 2T:

(2+6)Tmix=2(T)+6(2T)(2 + 6) T_{mix} = 2(T) + 6(2T)

8Tmix=2T+12T8 T_{mix} = 2T + 12T

8Tmix=14T8 T_{mix} = 14T

Tmix=148T=74TT_{mix} = \dfrac{14}{8}T = \dfrac{7}{4}T

Answer: 74T\dfrac{7}{4}T
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