A cylinder contains 20 kg of N2 gas M=28kgk−1mol−1at a pressure of 5 atm. The mass of hydrogen M=2kgk−1,mol−1 at pressure of 3 atm contained in the same cylinder at same temperature

VT=nRPn is number of moles; R is universal gas constant; P is pressure,volume V  and temperature T for  both cases in same Hencen1p1=n2p2 here n=massmolecular weight m1P1M1=m2P2M2    ;substitute given valuesm2=(3)(2)(5)(28)×20=0.86kg