MCQ
One mole of monatomic gas and three moles of diatomic gas are put together in a container. The molar specific heat (in $JK ^{-1} mol ^{-1}$ ) at constant volume is (Let $R=8 \,JK ^{-1} mol ^{-1}$ )
- ✓$18$
- B$19$
- C$20$
- D$21$
✓
Answer
Correct option: A.
$18$
a
(a)
(a)
$n_1=1 \text { mole } \quad f_1=3$
$n_2=3 \text { moles } \quad f_2=5$
$R=8 \,JK ^{-1} mol ^{-1}$
Molar specific heat are given by the weighted means of the gases.
$C_{v_f}=\frac{n_1 \times C_{v_1}+n_2 \times C_{v_2}}{n_1+n_2}$
$C_{v_f}=\frac{1 \times \frac{3}{2} R+3 \times \frac{5}{2} R}{4}$
$=\frac{3}{8} R+\frac{15}{8} R$
$=\frac{18}{8} R$
$C_{v_f}=18$
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