A student forgot to add a liquid in a round bottomed flask at 25°C. He placed the flask on the flame and recorded its temperature with a pyrometer which was found to be 327°C. Calculate the fraction of air that had gone out of the flask.

Since the mouth of flask was open, its pressure is equal to atmospheric pressure which is constant. So, the Charle's law is obeyed.T1=25+273=298K, Volume =V1;T2=327+273=600K and volume =V2∴ V1T1=V2T2;V1V2=T1T2=298K600K=0.4971∴ Air left in the vessel =0.4971Hence volume of air gone out =1−0.497=0.503=0.503×100=50.3%