Today We Did Another Lab!!!

MOLAR VOLUME LAB

Problem: To experimentally determine the molar volume of a gas

Materials:

§  Lighter (Butane)

§  Sink

§  Water

§  100 mL graduated cylinder

§  Weigh scale

Hypothesis: We expect to come to the conclusion that the molar volume of Butane at STP is 22.4 L/mol

Pre Lab:

1.      What is the chemical formula for Butane?

                        C₄H₁₀

        2.   Determine the molar mass of butane.

                        4(12.0) + 10(1.0) = 58 g/mol

Procedure:

1.      Weigh lighter and record weight.

2.      Fill sink with warm water.

3.      Submerge graduated cylinder in water making sure to release all air bubbles trapped in the cylinder by slightly tilting the opening of the tube to the surface of the water.

4.      stand the cylinder up vertically with the bottom of the tube out of the water and the opening still under the water. Tilt the tube making space for your lighter to be inserted.

5.      Insert the lighter and hold the red button down releasing Butane gas into the cylinder.

6.      Fill the cylinder with 100 mL of Butane.

7.      Remove lighter from cylinder and shake off excess water.

8.      Place lighter in a 40°C incubator for approximately 20 minutes making sure that all the water is removed.

9.      After 20 minutes remove the lighter from the incubator and re-weigh the lighter.

Observations:

§  Mass of lighter before - 21.10 g

§  Mss of lighter after - 20.88 g

§  Difference between masses - 0.22 g

§  As we released the gas the Butane rose to the top of the tube and pushed the water out

Analysis:

1.      What was the mass of the Butane lighter before the experiment? 21.10 g

2.      What was the mass of the Butane lighter after the experiment? 20.88 g

3.      What was the mass of the Butane used in the experiment? 0.22 g

4.      How many moles of Butane is in the mass in question 3? (0.22) x (1mol /58g) = 0.0038 mol

5.      Determine the molar volume of Butane. (0.100L /0.0038mol) = 26 L/mol

Conclusion:

1.      What is the percent error in your calculation of molar volume?

            [ (Experimental value - accepted value) / (experimental value) ] x 100 = Percent error

            [ (26 - 22.4) / (26) ] x 100 = 6.5%

2.      What factors may have affected your results?

            - The experiment was not conducted at STP (0°C, 101.3 KPa) therefore the gas occupied more volume that it would if it was at STP.

-Nicole