an experiment is performed to measure the mass percent of caco3(s) in eggshells. five different samples of caco3(s) of known mass react with an excess of 2.0mhcl(aq) in identical sealed, rigid reaction vessels. the pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. the experimental data are used to create the calibration line below.