A 5,00 m3 steel tank has a mass of 125.0 kg when placed under vacuum. It injects a pure gas until the pressure gauge shows 450.0 kPa; the temperature...

A 5,00 m3 steel tank has a mass of 125.0 kg when placed under vacuum. It injects a pure gas until the pressure gauge shows 450.0 kPa; the temperature remains stable at 17 ° C. After injection of the gas, the mass of the tank is 175.2 kg. The air pressure is 100 kPa. 

(a) how many moles of gas was injected? 

(b) what is the molar mass of the gas injected? 

(c) a second gas injected until the relative pressure of 725 kPa, what is 

the molar fraction of the first gas in the mixture?