Numerical answer type, answer in g, tolerance 0.5.
Answer: 43 g
Volume of O3 = 20 L (volume % = mole %), so n(O3) = 20/22.4 = 0.8929 mol. Mass absorbed = 0.8929 x 48 = 42.86 g, i.e. 43 g to the nearest integer. (For reference the average M of the original mixture is 0.2 x 48 + 0.8 x 32 = 35.2.)