1. [2] Calculate the number of moles of Mg you obtained (2.05 grams = 100 cm). n = m / M -> n (moles)= 2.05/24.3 (molar mass of magnesium) = .0843 moles 2. [2] Calculate the volume of hydrogen gas you should have collected in the lab. 2.05 x 1 mole Mg/24.3 g Mg x 1 mole H2/1 mole Mg = .0843 moles of hydrogen3. [2] What is the water vapor pressure? At 17 room temperature, the water vapor pressure is approximately 14.6 mmHg.4. [2] Calculate the volume of dry hydrogen gas at STP.101.9 kPa = 764.31275 mmhg. Thus, we must subtract water vapor pressure in order to get the volume of dry hydrogen gas at STP. As such, the answer is 749.71 mmHg. 5. [2] Calculate the molar volume of hydrogen using the answer from question #4.271.2633 mL = 0.2712633 L -> .27 L (273/290) (749.71/764)= 248724 L Patm = PH2 + PH20 (DALTONS LAW)