Molar Volume of Hydrogen Lab

Experiment Overview:
The purpose of this experiment is to determine the volume of one mole of hydrogen gas at standard temperature and pressure (STP).  Hydrogen will be generated by the reaction of know mass of magnesium with excess hydrochloric acid in an inverted graduated cylinder filled with water.  The volume of hydrogen collected by water displacement will be measured and corrected for differences in temperature and pressure in order to calculate the molar volume of hydrogen at STP.

6

Fill in the data as we go, if you miss something ask immediately or wait and watch the video recording.

3

Calculate the theoretical numbers of moles of hydrogen gas produced in trials 1 and 2. Start with the mass of Mg used in each trial.

3

Use Table 1 to find the vapor pressure of water at the temperature of the water bath in this experiment. Calculate the partial pressure of hydrogen gas produced in tirals 1 and 2. Remember PT is barometric pressure.

4

Use the combined gas law to convert the measured volume of hydrogen to the volume the gas would occupy at STP for trials 1 and 2. (remember to use the corrected volume and watch those units!)

2

Divide the volume of hydrogen gas at STP by the theoretical number of moles of hydrogen gas to calculate the molar volume of hydrogen for trials 1 and 2. (You have already calculated the volume of hydrogen gas at STP, this needs to be in Liters, and the theoretical # of moles, now just divide those two values.)

2

Average the molar volumes for your two trials.

3

Calculate the percent error using your average molar volume from the previous calculation and the know molar volume at STP. If you don't remember the known value ( 1 mole of any gas at STP = _____L) then look it up :)
|known value - your calculated value| x 100
known value

2

In setting up this experiment, a student noticed a bubble of air leaked into the graduated cylinder when it was inverted in the water bath.
a) What effect would this have on the measured volume of hydrogen gas?

3

Fill in the data as we go, if you miss something ask immediately or wait and watch the video recording.

Calculate the theoretical numbers of moles of hydrogen gas produced in trials 1 and 2. Start with the mass of Mg used in each trial.

Use Table 1 to find the vapor pressure of water at the temperature of the water bath in this experiment. Calculate the partial pressure of hydrogen gas produced in tirals 1 and 2. Remember PT is barometric pressure.

Use the combined gas law to convert the measured volume of hydrogen to the volume the gas would occupy at STP for trials 1 and 2. (remember to use the corrected volume and watch those units!)

Average the molar volumes for your two trials.

Calculate the percent error using your average molar volume from the previous calculation and the know molar volume at STP. If you don't remember the known value ( 1 mole of any gas at STP = _____L) then look it up :)|known value - your calculated value| x 100 known value

In setting up this experiment, a student noticed a bubble of air leaked into the graduated cylinder when it was inverted in the water bath. a) What effect would this have on the measured volume of hydrogen gas?

b) Would the calculated molar volume of hydrogen be too high or too low as a result of this error? (support your answer)

Calculate the percent error using your average molar volume from the previous calculation and the know molar volume at STP. If you don't remember the known value ( 1 mole of any gas at STP = _____L) then look it up :)
|known value - your calculated value| x 100
known value

In setting up this experiment, a student noticed a bubble of air leaked into the graduated cylinder when it was inverted in the water bath.
a) What effect would this have on the measured volume of hydrogen gas?