An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pres…

Question

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 After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressure at temperature 27°C. The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given, R=100/12 J mol^-1K^-1, molecular mass of O2 = 32, 1 atm =1.01×10^5 N/m^2]

1. A. 0.125 kg
2. B. 0.144 kg
3. C. 0.116 kg (Correct answer)
4. D. 0.156 kg

Correct Answer

Option C — 0.116 kg

Detailed Solution & Explanation

The correct answer is 0.116 kg.

Key Points

• Absolute pressure after withdrawal $=11+1=12$ atm. Moles left: $n=\dfrac{PV}{RT}=\dfrac{12\times1.01\times10^{5}\times30\times10^{-3}}{\frac{100}{12}\times300}=14.54$ mol.
• Moles withdrawn $=18.2-14.54=3.656$ mol.
• Mass withdrawn $=3.656\times32\approx116.99$ g $\approx 0.116$ kg.