mole fraction of oxygen = no.of moles of oxygen /(no.of
moles of oxygen +no.of mole of nitrogen)
                                           Â
= 4/(4+2)
                                             Â
= 4/6
                                          Â
= 0.67
     partialpressure of oxygen
= total pressure * mole fraction of oxygen = 6*0.67 = 4.02
atm
                                     Â