please answer correctly

Sometimes in lab we collect the gas formed by a chemical reaction over water (see sketch at right). This makes it easy to isolate and measure the amount of gas produced. Suppose the CO gas evolved by a certain chemical reaction taking place at 30.0C is collected over water, using an apparatus something like that in the sketch, and the final volume of gas in the collection tube is measured to be 99.8mL. Calculate the mass of CO that is in the collection tube, Round your answer to 2 significant digits. You can make any normal and reasonable assumption about the reaction conditions and the nature of the gases