A gas of mass 2 g occupies a volume of 820 ml at 7°C temperature and 2 atm pressure. Determine the molar mass of the gas. [R = 0.082 L atm mole⁻¹ K⁻¹]
WBBSE
Class X
Physical Science
Behaviour of Gases
02 Mark
2026
Mass of gas (m) = 2 g
Volume (V) = 820 ml = 0.820 L
Temperature (T) = 7°C = 280 K
Pressure (P) = 2 atm
Gas constant (R) = 0.082 L atm mol⁻¹ K⁻¹
From Ideal Gas Equation: PV = nRT
Number of moles (n) = \frac{\text{PV}}{\text{RT}}
= \frac{2\times0.820}{0.082\times280}
= 0.0714 mol
Molar mass (M) = \frac{\text{Mass}}{\text{Number of moles}}
= \frac{2}{0.0714}
= 28 g mol⁻¹
Hence, the molar mass of the gas is 28 g mol⁻¹.
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