Question

Find the loss in the mass of 1 mole of an ideal monatomic gas kept in a rigid container as it cools down by 100°C. The gas constant R = 8.3 J K⁻¹ mol⁻¹.

Answer 1

Given: Number of moles of gas, n = 1

Change in temperature, ∆T = 10°C

Energy possessed by a mono atomic gas,

\[E = \frac{3}{2}nRdT\]

Now,

\[R = 8.3 J/mol -K\]

This decrease in energy causes loss in mass of the gas. Thus,

Loss in mass, \[∆ m = \frac{Q}{c^2}\]

\[\Rightarrow ∆ m = \frac{1 . 5 \times 8 . 3 \times 10}{c^2}\]
\[ = \frac{124 . 5}{9 \times {10}^{16}} = 1 . 38 \times {10}^{- 15} kg\]