PV = n RT= (m/M) RT

M= dRT /P

=1.15 x .0821 x 300/ 700 /760 = 30.75gmol^{-1}

Let w1 be the mass fraction of N2 ans 1- w2 is the mass fraction of O_{2}

so w_{1} X28 + (1- w_{1} )X 32 = 30.75

w_{1} = 0.3125

% compostion of N_{2 }= 31.25 %

% composition of O_{2} = 68.75 %