An evacuated glass vessel weighs 40.0 g when empty, 135.0 g when filled with a liquid of density 0.95 g mL–1 and 40.5 g when filled with an ideal gas at 0.82 atm at 250 K. The molar mass of the gas in g mol–1 is: (Given : R = 0.082 L atm K–1 mol–1)
- 35
- 50
- 75
- 125
The Correct Option is D
Solution and Explanation
Weight of liquid = 135.0 – 40.0 = 95.0 g
Volume of liquid=\(\frac{95}{0.95}\)=100ml =0.1L
Weight of gas = 0.5 g
Moles of gas\(=\frac{0.5}{M}\)
\(PV = nRT\)
\(0.82×0.1=\frac{0.5}{M}×0.082×250\)
\(M=0.5\times250=125\) g mol-1
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Concepts Used:
Ideal Gas Equation
An ideal gas is a theoretical gas composed of a set of randomly-moving point particles that interact only through elastic collisions.
What is Ideal Gas Law?
The ideal gas law states that the product of the pressure and the volume of one gram molecule of an ideal gas is equal to the product of the absolute temperature of the gas and the universal gas constant.
PV=nRT
where,
P is the pressure
V is the volume
n is the amount of substance
R is the ideal gas constant
Ideal Gas Law Units
When we use the gas constant R = 8.31 J/K.mol, then we have to plug in the pressure P in the units of pascals Pa, volume in the units of m3 and the temperature T in the units of kelvin K.