Question

Propylene oxide is a common liquid compound that vaporizes readily. Determine the molar mass of propylene oxide from the following data:


Sample mass = 0.0780 g Volume of gas = 125 mL

Temperature = 0.0 °C Pressure = 183 mm Hg

Molar mass =______ g/mol

Answer 1

$M=m/n$ , n - chemical amount of substance(mol); m - mass of substance(g); M - molar mass of substance(g/mol).

$PV=nRT$ , P - gas pressure (Pa) , V - gas volume (m³), n - chemical amount of gas (mol), T - temperature of gas (K), R - Gas constant (8,314 J/(mol*K)).

express n: $n=PV/RT$

V=125ml=125cm³=1,25*10^-4m³

T=0,0oC=273,15K

P=183mmHg=24398Pa

n=(24398Pa*1,25*10^-4m³)/(8,314J/(mol*K)*273,15)=0,0013mol

M=0,0780g/0,0013mol=58g/mol

Answer:58g/mol