LAB: THE MOLAR VOLUME OF A GAS ANSWERS

Introduction: When magnesium reacts with hydrochloric acid, hydrogen gas is produced. The gas can be collected in a eudiometer where its volume may be determined. Knowing the number of moles of magnesium used, we can calculate the volume of hydrogen produced per mole of magnesium used. The balanced equation for this reaction allows us to determine the molar volume of a gas at standard temperature and pressure.

Purpose: How much volume does one mole of gas occupy at standard temperature and pressure (STP)?

QUESTIONS:
1. Why did we measure the length of the magnesium and use the grams per meter to calculate the moles rather than just weighing the magnesium?

A: The length was measured instead fore more precise data because the Mg was very small, and there were more variables that could have altered the results, measuring the length would provide fore better calculations in terms of accuracy and precision. 

2. The assumption made in this lab is that there was 100% yield of hydrogen gas. Did any bubbles escape out the bottom? Did all your magnesium react? How would the final results have been affected if there had been less than 100% yield?

A: Yes a few bubbles escaped out of the bottom, and yes all the Mg reacted because HCL was the excess reactant. If there had been less than 100 percent yield, the the molar value would be higher. 

3. How likely was it that 100% yield was obtained? (how likely is it ever that 100% yield is obtained?)

A: Not very likely because all the bubbles in the tube cannot be tapped out. 

4. Why did we correct the pressure by measuring the height differences?

A: The height difference needed to be corrected because after the reaction occurred there was a height difference, and you cant measure the pressure inside the tube so the height difference was subtracted from the pressure in the room to get a new total pressure. 

5. If you had not corrected for the fact that the gas collected in this lab was wet, how would your final result have been affected?

A: The molar volume would be higher because wet gas weighs more.