Question

A 3.25 g3.25 g sample of an unknown gas at 69 ∘C69 ∘C and 1.00 atm1.00 atm is stored in a 1.05 L1.05 L flask.

What is the density of the gas?

What is the molar mass of the gas?

Answer 1

Let us assume that the gas follows the ideal gas equation: PV=nRT Where, P=pressure, V=volume, n=number of moles, T= temperature and R= Universal Gas Constant Given: P= 1 atm, V=1.051, T=69°C=342.15 K Amount of the gas=m=3.25 g We know, n=m/M, where M= molar mass of the gas PV=(m/MRT, P=(m/V)(RT/M) = dRT/M, where d=m/V; density of the gas. R=0.08206 L atm K-Imol-1 d=m/V=3.25 g/1.05 L = 3.10 g L- M=dRT/P=(3.10 g L-1 x 0.08206 Latm k-mol-2 x 342.15 K)/1 atm =87.04 g mol-1