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Molar Volume of an Ideal Gas

Add 0.25g of zinc to the Erlenmeyer flask and close the flask with an air-tight stopper. Take a thermometer and pressure gauge and record the initial temperature and pressure.(my answer: 21C, 1 atm). Add 10 mL of 6M HCl solution to the flask. Record all of the indications that the reaction has occurred (my answer: temperature above 30C, 1.729 atm). Once the flask has cooled down to room temperature (21C), drop the flask onto the gas piston. This connects the two and allows gas to flow from the flask into the gas piston until the pressure equalizes. What pressure is that (my answer: 1 atm?) Record the volume of gas that is contained in the gas piston (my answer: 102.14mL )

Repeat the experiment with a new flask and gas piston, using 0.5g of zinc and 10 mL of HCl. Record all of the indications that the reaction has occurred (my answer: temperature above 40C, 2.386 atm). Drop the flask onto the gas piston to allow gas to flow from the flask into the gas piston until the pressure equalizes. What pressure is that (my answer: 1 atm?) Record the volume of gas that is contained in the gas piston (my answer: 194.28mL )

1. Record and calculate the following for the first half of the experiment:

(a) Mass of zinc used (g): 0.25g
(b) Volume of 6M HCl used (mL): 10mL
(c) Molecular weight of zinc (g/mol): 65.39g/mol
(d) Moles of zinc reacted: 0.0038 moles
(e) Moles of hydrogen produced: 0.00382 moles
(f) Molar volume of the ideal hydrogen gas at room temperature (Volume/moles), expressed as L/mol at X degrees C and a pressure of 1 atm.

2. For the second part of the experiment, everything was the same except that twice as much Zn was used.

(a) Mass of zinc used (g): 0.50g
(b) Volume of 6M HCl used (mL): 10mL
(c) Molecular weight of zinc (g/mol): 65.39g/mol
(d) Moles of zinc reacted: (just half will react?)
(e) Moles of hydrogen produced: (is it the same as in the first experiment?)
(f) Molar volume of the ideal hydrogen gas at room temperature (Volume/moles), expressed as L/mol at X degrees C and a pressure of 1 atmosphere.

3. Compare the molar volumes obtained in the two parts of the experiment. What difference did using twice the amount of Zn in the second part? Was all of the zinc used up in the reaction? Which is the limiting reactant - zinc or HCl?

4. Compare the experimental value for the molar volume at 21C with the accepted value. Calculate the experimental error according to

% error = | experimental molar volume - listed molar volume | / (listed molar volume) * 100

Solution Preview

The balanced chemical equation for this reaction is:
Zn + 2 HCl -> H2 + ZnCl2

In your first experiment, you used .0038 moles of zinc. This amount of zinc would react with .0076 moles of HCl if it were to react 100%. There were .06 moles of HCl present which are much more than enough to react with all of the zinc. So the limiting reactant in the first experiment was zinc.

In the second experiment, you used .0076 moles of zinc. This would require .0152 moles of HCl to completely react. Again, there were .06 moles of HCl present, so again, zinc is the limiting reactant.

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Solution Summary

The limiting reactant is determined. Calculations calculating moles of reactants and products from mass are used for all determinations. A discussion of expected results verses actual results and causes for deviation are discussed.

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