How many mLs of H_2O gas, collected by water displacement, are produced by the reaction of 0.500 g of Mg metal with an excess of HCI, at an atmospheric pressure of 750 torr and a temperature of 25.0 degree C? The vapour pressure of water at 25.0 degree C is 23.8 torr. answer _________________ Given the following reaction: 2KCIO_3(s) rightarrow 2 KCl(s) + 3 O_2(g) What mass of KClO_3 will produce 250 mL of O_2 gas, collected by water displacement, at an atmospheric pressure of 745 torr and a temperature of 30.0 degree C? The vapor pressure of water at 30.0 degree C is 31.8 torr.