A cylinder of compressed gas contains nitrogen and oxygen in the ratio 3:1 by mole. If the cylinder is known to contain 2.5×104 g of oxygen, what is the total mass of the gas mixture?

Number of moles of oxygen in the cylinder = = Mass (in gram)  Molecular mass (in gram mol-1=2.5×10432=781.25∴  Number of moles of N2=3×781.25=2343.75Mass of nitrogen in the cylinder = 2343.75×28                                              = 65625 g = 6.5625x 104gTotal mass of the gas in the cylinder =2.5×104+6.5625×104                    =9.0625×104 g