Medium MCQ +4 / -1 PYQ · JEE Mains 2020

Two moles of an ideal gas with ${{{C_P}} \over {{C_V}}} = {5 \over 3}$ are mixed with 3 moles of another ideal gas with ${{{C_P}} \over {{C_V}}} = {4 \over 3}$. The value of ${{{C_P}} \over {{C_V}}}$ for the mixture is :

  1. A 1.50
  2. B 1.45
  3. C 1.47
  4. D 1.42 Correct answer

Solution

C<sub>p</sub> = ${{{n_1}{C_{{p_1}}} + {n_2}{C_{{p_2}}}} \over {{n_1} + {n_2}}}$ <br><br>C<sub>v</sub> = ${{{n_1}{C_{{V_1}}} + {n_2}{C_{{V_2}}}} \over {{n_1} + {n_2}}}$ <br><br>$\gamma$<sub>mix</sub> = ${{{C_p}} \over {{C_v}}}$ = $${{2 \times {5 \over 2}R + 3 \times {8 \over 2}R} \over {2 \times {3 \over 2}R + 3 \times {6 \over 2}R}}$$ <br><br>= ${{5 + 12} \over {3 + 9}}$ = 1.42

About this question

Subject: Physics · Chapter: Thermodynamics · Topic: Zeroth and First Law

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