Q99 / 180 · NEET 2025 · Physics
An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressure at temperature $27^{\circ} \mathrm{C}$. The mass of the oxygen withdrawn from the cylinder is nearly equal to :
[Given, $R=\frac{100}{12} \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$, and molecular mass of $O_2=32,1 \mathrm{~atm}$ pressure $\left.=1.01 \times 10^5 \mathrm{~N} / \mathrm{m}\right]$
- A$0.125 \mathrm{~kg}$
- B$0.144 \mathrm{~kg}$
- Correct answerC$0.116 \mathrm{~kg}$
- D$0.156 \mathrm{~kg}$
Solution
$\begin{aligned} & \mathrm{n}_{\mathrm{f}}=\frac{\mathrm{P}_{\mathrm{f}} \mathrm{V}}{\mathrm{RT}} \quad\left[\mathrm{P}_{\mathrm{abs}}=12 \mathrm{~atm}\right] \\ & =\frac{12 \times 1.01 \times 10^5 \times 30 \times 10^{-3}}{\left(\frac{100}{12}\right) \times 300} \\ & =14.544 \\ & \therefore \text { moles removed }=18.2-14.544=3.656 \\ & \therefore \text { mass removed }=3.656 \times \frac{32}{1000} \mathrm{~kg}=0.116 \mathrm{~kg}\end{aligned}$
Hence, the correct answer is option: 'C'.