Question

Calculate the molar mass of a gas at 506 torr and 99°c if 206 ng of gas occupies 0.206 ul. (

Answer 1

PV = nRT  

and n = mass / mw  

PV = (mass / mw) RT  

mw = mass RT / PV  

P = 352 torr = 352 torr x (1 atm / 760 torr) = 0.463 atm  

V = 0.206x10^-6 L  

R = 0.0821 L atm /moleK  

T = 45C = 45+273 = 318 K  

mass = 243x10^-9 g  

mw = (243x10^-9 g)x(0.0821 L atm /moleK)x(318 K) / [(0.463 atm)x(0.206x10^-6 L)]  

mw = 66.5 g/mole