Phychem notes- Gases Problem solving # 3

For a cetain gas, 20.0 mg exerts a pressure of 24.7 Torr in a 500 cm3 vessel at 25 degrees Celsius. Find the molar mass.




solution
Mx = 20.0 mg  Px= 24.7 torr Vx= 500 cm3  T= 25C+ 273K= 298 K
M=?

 n= PV/RT= 24.7 torr (0.500L)/ 62.364 L torr /K.mol (298K)  = 0.000665 mol

n=m/M= .0200 g/0.000665 mol= 30.0 g/mol