When 2 g of a gas is introduced into an evacuated flask kept at 25∘C, the pressure is found to be 1 atmosphere. If 3 g of another gas B is then added to the same flask, the total pressure becomes 0.5 atmosphere. Assuming ideal gas behaviour, calculate the ratio of molecular mass MA:MB.
1:3
Applying ideal gas equation n moles,
PV= nRT,
PV=gMRT⇒M=gRTPV
Let the molecular mass of two gases be MA and MB
Therefore, MA=2×RT1×V and MB=3×RT0.5×V
⇒MAMB=2RTV×0.5V3RT=2×0.53=13
Ratio of molecular mass MA:MB=1:3