You have an evacuated container of fixed volume and known mass and introduce a known mass of a gas sample. measuring the pressure at constant temperature over time, you are surprised to see it slowly dropping. you measure the mass of the gas-filled container and find that the mass is what it should be - gas plus container - and the mass does not change over time, so you do not have a leak. part a suggest an explanation for your observations. suggest an explanation for your observations. the gas undergoes a chemical reaction that has fewer gas particles in products than in reactants. pressure is directly proportional to number of particles, so the pressure decreased. when the gas was plased into container it obtained some extra kinetic energy. after some time this energy was expend, so the speed of the particles reduced and the pressure dropped the gas undergoes a chemical reaction that has more gas particles in products than in reactants. pressure is directly proportional to number of