An evaluation of r was performed, following the procedure described in this module. the barometric pressure was 736 torr, the temperature was 295k and volume of hydrogen gas collected was 35.6 ml. the calculated value of r was 82.1 ml atm k-1 mol-1. 1) how many grams of magnesium metal were used? 2) if the vapor pressure of water had not been taken into account, what would have been the calculated value of r? 3) if the springe volume had been incorrectly read, giving a calculated system volume of 25.6 ml, what would have been the percent error in the calculated value of r?