Question

The kinetic energy of translation of 20 gm of oxygen at 47°C is (molecular wt. of oxygen is 32 gm/mol and R = 8.3 J/mol/K)

• A. 2490 joules
• B. 2490 ergs
• C. 830 joules
• D. 124.5 joules

Answer 1

Answer: (A)

2490 joules

Answer 2

Kinetic energy for m gm gas $E = \frac{f}{2}mrT$

If only translational degree of freedom considered then

$f = 3$Ž $E_{\text{Trans}} = \frac{3}{2}mrT = \frac{3}{2}m\left( \frac{R}{M} \right)T$

$= \frac{3}{2} \times 20 \times \frac{8.3}{32} \times (273 + 47) = 2490J$