Active mass of eight grams of oxygen at STP is

At STP a mole of O2​ will occupy 22.4l of volume.moles of O2​=8​/32=0.25Active mass = conc. in mol  L−1Volume = 1 mole of O2​= 22.4l0.25 mole of O2​  =22.4​ × 0.25  = 5.6lActive mass of O2​ = 0.25/5.6​ =  0.0446mole/L