For estimating ozon in the air, a certain volume of air is passed through an acidified or neutral KI solution when oxygen is evovled and iodide is oxidized to give iodine. when such a solution is acidified , free iodine is evolved which can be titrated with standard Na2S2O3 solution. in an experiment 10 litre of air at 1 atm and 27*c were passed through an alkaline KI solution , at the end the iodine entrapped in a solution an titration as above required 1.5 mL of 0.01 N Na2S2O3 solution. calculate volume % of O3 in sample.