7 g of nitrogen and 4g of oxygen are confined in a total volume of 1.5 litre at 0∘C. Calculate the total pressure of gases in the vessel.

1 mol or 28 g N2 occupy volume at 1 atm pressure and 0∘C=22.4L 7 g N2 will occupy volume =22.4L28g×7g=5.6L1 mol or 32 g O2 occupy volume at 1 atm pressure and 0∘C=22.4L4g of O2 occupy volume=22.4L32g×4g=2.8LFor N2:    P2=P1V1V2=1atm×5.6L1.5L=3.73atm.O2:    P2=P1V1V2=1atm×2.8L1.5L=1.87atm.∴ Total pressure =3.73atm+1.87atm=5.60atm.