Calculating the Molar Volume of a Gas Experiment.

% uncertainty for Vapor Pressure = 0%

% uncertainty for Partial Pressure = 0. 489%

% uncertainty to absolute uncertainty = 0. 489*100.0/100 = ±0. 489

∴ Absolute uncertainty of Partial Pressure = 100.000 kPa ±0. 489

Volume occupied by one mole of hydrogen at STP

P1V1/T1 = P2V2/T2

100*0.037/292 = 100*V/273

V = 0.0346 dm3

% uncertainty for Pressure 1 = 0. 489%

% uncertainty for Volume 1 = 0.0005/0.037*100 = 1.35%

% uncertainty for Temperature 1 = 0.5/292*100 = 0.171%

% uncertainty for Pressure 2 = 0%

% uncertainty for Temperature 2 = 0%

% uncertainty for Volume 2 = 0.489+0.171+1.35 = 2.01%

% uncertainty to absolute uncertainty for Volume 2 = 2.01*0.0346/100 = 0.000696

∴ Absolute uncertainty for Volume = 0.034600 dm3 ±0.000696

Molar Volume

Moles = Volume/Molar Volume

0.00146 = 0.0346/Molar Volume

Molar Volume = 23.7 dm3/mol

% uncertainty for Volume = 2.01%

% uncertainty for Moles = 0.01%

% uncertainty for Molar Volume = 2.01+0.01 = 2.02%

% uncertainty to absolute uncertainty for Molar Volume = 2.02*23.7/100 = ±8.52

∴ Absolute uncertainty for Molar Volume = 23.7 dm3/mol ±8.52

Molar Volume = 23.7 dm3/mol ±8.52

Trial 2

Partial Pressure of Hydrogen

Partial Pressure of Hydrogen = Atmospheric Pressure – Vapor Pressure

Partial Pressure of Hydrogen = 102.2 – 2.6

Partial Pressure of Hydrogen = 99.6 kPa

Volume occupied by one mole of hydrogen at STP

P1V1/T1 = P2V2/T2

99.6*0.0404/295 = 100*V/273

V = 0.0372 dm3

Molar Volume

Moles = Volume/Molar Volume

0.00146 = 0.0372/Molar Volume

Molar Volume = 25.5 dm3/mol

Average of both Trials = (25.5+23.7)/2 = 24.06

Evaluation

I assumed that the temperature inside the eudiometer is equal to the temperature of the surroundings which is why there was a certain degree of error in the results since they are not the same. Also during the experiment, when the stopper was inserted in the tube, covered with my finger and turned, a small air bubble remained in the tube. This resulted in the volume being larger than expected. I could have taken more precautions and done it slowly to make sure there are no air bubbles inside the tube. Some of the hydrogen started reacting with the magnesium ribbon as soon as the magnesium ribbon was put into the water. This resulted in some of the gas escaping from the tube.  Due to which, the value for the volume of hydrogen reduced hence resulting in us getting a value away from the expected value. I used ideal gas law to find the volume occupied by one mole of hydrogen at STP but hydrogen is not an ideal gas. To get better results, I could have done more trials.

Conclusion

The aim of the experiment was to find the molar volume of Hydrogen. I got 24.06 (average) as the volume of one mole of hydrogen at STP. In the first trial, the molar volume found is 23.7 dm3/mol with an uncertainty of ±8.52. In the second trial, the molar volume is 25.5 dm3/mol. The molar volume of the second trial is higher because the yield of hydrogen in the second trial was higher than the first. The temperature in the second trial was higher as well.  The theoretical results are 22.4 dm3. The difference is due to the errors made during the experiment and the assumptions I made.