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Question:

Two non-reactive monoatomic ideal gases have their atomic masses in the ratio 2:3. The ratio of their partial pressures, when enclosed in a vessel kept at a constant temperature, is 4:3. The ratio of their densities is?

1 : 2

6 : 9

8 : 9

1 : 4

Solution:

The correct option is D 8 : 9
Sol: (D) PV=nRT=mMRT → PM=ρRT
ρ1/ρ2 = P1M1/P2M2 = (P1/P2) × (M1/M2) = (4/3) × (2/3) = 8/9
Here ρ1 and ρ2 are the densities of the gases in the vessel containing the mixture.