How many moles of H₂O are in the system? — States of Matter and Gaseous State Chemistry Question

💡 Solution & Explanation

Initial total moles in A: $n = (570/760 \times 1.642) / (0.0821 \times 300) = 0.05 \text{ mol}$. After opening to B, pressure is 0.21 atm. $n_{gas} = P \times V_{bulb} \times (1/RT_A + 1/RT_B) = 0.21 \times 1.642 / 0.0821 \times (1/300 + 1/200) = 4.2 \times (5/600) = 0.035 \text{ mol}$. Moles of H₂O = $0.05 - 0.035 = 0.015 \text{ mol}$. Therefore, correct answer is B.