Q. The kinetic energy of translation of $20\ g$ of oxygen at $47℃$ is (molecular wt. of oxygen is $32\ g/mol\ $and R = $8.3J/mol/K$)
A) $2490\ joules$
B) $2490\ ergs$
C) $830\ joules$
D) $124.5\ joules$
Explanation
(a) Kinetic energy for $m\ g$ gas $E = \frac{f}{2}mrT$
If only translational degree of freedom is considered
Then $f = 3 \Rightarrow E_{Trans} = \frac{3}{2}mrT = \frac{3}{2}m\left( \frac{R}{M} \right)T$
$= \frac{3}{2} \times 20 \times \frac{8.3}{32} \times (273 + 47) = 2490J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.