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Physics · PYQ NEET UG 2025
हिन्दीAn oxygen cylinder of volume \( 30\text{ litre} \) has \( 18.20\text{ moles} \) of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to \( 11\text{ atmospheric pressure} \) at temperature \( 27^\circ\text{C} \). The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given, \( R = \frac{100}{12}\text{ J mol}^{-1}\text{K}^{-1} \), and molecular mass of \( O_2 = 32 \), \( 1\text{ atm pressure} = 1.01 \times 10^5\text{ N/m}^2 \)]
Correct answer · Option 3
\( 0.116\text{ kg} \)
Explanation
Absolute pressure \( P = 11 + 1 = 12\text{ atm} \). Remaining moles \( n_2 = \frac{PV}{RT} = \frac{12 \times 1.01 \times 10^5 \times 30 \times 10^{-3}}{(\frac{100}{12}) \times 300} \approx 14.54\text{ moles} \). Moles withdrawn \( \Delta n = 18.20 - 14.54 = 3.66\text{ moles} \). Mass \( = 3.66 \times 32 \approx 117\text{ g} = 0.117\text{ kg} \approx 0.116\text{ kg} \).
