1. Determination of the Molar Volume of H2 Gas
Lab 9

2. Equipment Setup
Today you will set up your equipment and run your experiment prior to the pre-lab lecture.
After you are finished, return to your seats.
Here’s how to proceed:

3. Equipment Weigh out a Mg strip Roll into a ball
Insert into alligator clip

4. Equipment Continued
Carefully add 10 mL of 6M HCl to the eudiometer tube.
Fill the tube carefully with distilled water.
Place the stopper in the tube and eliminate all air bubbles.

5. Equipment Continued
With your finger over the hole in the stopper, invert the tube and place in 100 mL dH2O.
Clamp the tube to a buret clamp.
The stopper should be mm from the bottom.
Record the time.

6. Equipment Continued
Record the volume of H2 gas from your eudiometer tube after 1 hour.
Go ahead…

7. Purpose
The molar volume of all gases at STP is L/mol. In this experiment, we will be collecting H2 gas by displacement of water to determine the molar volume of H2 gas experimentally, i.e. confirm that it is L/mol. Note the slight deviation from ideal behavior.

8. Discussion
Physical properties of gases can be related through mathematical equations, known as laws:
For Single Gases -
Boyle’s Law: V = ; at constant T and n
Charles’ Law: V = bT; at constant P & n
Avogadro’s Law: V = an; at constant T and P
Ideal Gas Law: PV = nRT
For Mixed Gases -
Dalton’s Law: PT = P1 + P2 + P3 …

9. Reaction
The net ionic equation for this redox reaction is: 2H+(aq) + Mg(s)  Mg2+(aq) + H2(g) reduced oxidized

10. Data Accepted Molar Volume is 22.433 L/mol
Atmospheric Pressure can be obtained from the barometer
Vapor Pressure of Water in mmHg is obtained from Table 9.1
Water Bath Temperature in degrees Celsius is obtained using the digital thermometer
The pressure difference in mm H2O is measured with a meter stick.
Mass of Magnesium is obtained from the balance

11. Data Continued Partial Pressure of H2 gas in mmHg from Dalton’s law.
Volume of H2 gas is obtained from your Eudiometer tube.
Volume of H2 gas at STP is obtained from:
Example: = =

12. Data Continued Theoretical moles of H2 are obtained from: moles H2 =
Molar Volume of H2 gas is obtained from:
molar VolH2 =

13. Safety Concerns Reagents: Eye Contact: Skin Contact: Ingestion:
Hydrochloric Acid
Magnesium Metal
Eye Contact:
irreversible damage, severe burns, painful sensitization to light
Skin Contact:
Burns, rash, and ulceration
Ingestion:
digestive tract burns, circulatory system failure, abdominal pain, diarrhea, vomiting, and death
Inhalation:
sore throat, coughing, shortness of breath, lung edema, burns, erosion of teeth, damaged mucosa, chest pain, fever, and leukocytosis

14. Waste
Acidic solutions / waste need to be disposed in the acid waste container in the fume hood.

15. Lab 10 Reminder
Lab 10 is next.