Q. The kinetic energy of translation of $20\, g$ of oxygen at $47^{\circ} C$ is (molecular wt. of oxygen is $32 \,g / mol$ and $R =8.3\,J / mol / K$ )

Kinetic Theory Report Error

A

2490 joules

B

2490 ergs

C

830 joules

D

124.5 joules

Solution:

Kinetic energy for $m g$ gas $E=\frac{f}{2} m r T$
If only translational degree of freedom is considered Then $f=3$
$ \Rightarrow E_{\text {Trans }}=\frac{3}{2} m r T=\frac{3}{2} m\left(\frac{R}{M}\right) T$
$=\frac{3}{2} \times 20 \times \frac{8.3}{32} \times(273+47)=2490 J$

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