Agas mixture contains each of the following gases at the indicated partial pressures: , 221o2torr , n2,131 torr; and he 131 torr
what mass of each gas is present in a 1.30 - l sample of this mixture at 25.0 degrees c?

 221 torr + 131 torr + 131 torr = 483 torr total 
n = PV / RT = (483 torr) x (1.30 L) / ((62.36367 L Torr/K mol) x (25.0 + 273.15 K)) = 0.033769 mol gases total 
(0.033769 mol) x ( 221 torr N2/ 483 torr) x (28.01344 g N2/mol) = 0.433 g N2 
(0.033769 mol) x (131 torr O2/ 483 torr) x (31.99886 g O2/mol) = 0.293 g O2 
(0.033769 mol) x (131 torr He/ 483 torr) x (4.0026 g He/mol) = 0.0367 g He