Molar Volume and the Universal Gas Constant

Experiment 6: Molar Volume and the Universal Gas Constant

Statement of Purpose

In the experiment, we had to determine the volume of hydrogen gas that is produced when a sample of magnesium metal reacts with hydrogen chloride dissolved in water. As a result, we were able to calculate the molar volume of hydrogen. Theoretically, we will now be able to calculate the molar volume of any gas now.

Summary of Procedure

Our first procedure was to obtain a small strip of magnesium and fold it so it can be encased in a small spiral cage made of thin copper wire. Next, we set up a ring stand and utility clamp in position to hold a 50 mL gas measuring tube that would be fitted with a one-hole stopper. We also filled a beaker ⅔ full of water under it. Next, we tilted the tube and placed 10 mL of hydrochloric acid with 1 mL of red colour to identify it and poured the water from the beaker till it over flowed into the gas measurement tube. Next, we added the copper wire cage into the water with a hook so it wouldn't drop to the bottom. We then put 1 finger over the top with the one-hole stopper and flipped it. The acid then moved down and reacted with the magnesium. After 5 minutes, we dislodged any air bubbles that were left over on the side of the tube and transported the tube into a large jar filled with room temperature water (covering the top with a finger the whole time. We raised or dropped the gas tube so both meniscus’ were the same level; we measured the volume of gas. Lastly, after removing the tube, we poured out the contents and cleaned up the lab.

Observations

Beginning of Reaction

bubbles(rising up)

Red color starts to move down towards the magnesium

Fizzing around magnesium

Before Reaction

Dense solution of dye and hydrochloric acid

No air pockets

“Air” bubbles on the side of the gas tube(reaction probably already started w/o me noticing)

Data

Length of Magnesium

2.30 cm

Volume of Hydrogen Gas

42.0 mL

Room Temperature

25℃

Room Pressure

74.5 cm

Volume of Hydrogen Chloride

10.0 mL

Results and Questions

1. The mass of the magnesium ribbon is 0.0375 grams.

Mg ribbon=1.6299 g/meter 2.3cm=0.023 meters 1.6299/1m=0.0375 g/meter

2. The number of moles of magnesium used is 0.00154 moles.

0.0357g Mg(1 mol/24.3g)=0.00154 mol Mg

3. The partial pressure of the hydrogen gas is 721.2 torr.

Room Pressure=745 745-23.76=721.24 torr

4. The volume of the hydrogen gas if collected at 1 atm would have been 39.9 mL.

(P1)(V1)=(P2)(V2)→(721.24/760)(42 mL)=(1)(V2) V=39.858

5. The volume of the hydrogen gas that would have been occupied at standard pressure is 36.5 mL.

V1/T1=V2/T2 39.858/298=V2/273 V=36.51 mL

6. The volume the hydrogen gas would have occupied with 1 mole of magnesium is 23,703 mL.

V1/n1=V2/n2 36.51/0.00154=V2/1 V=23,702.8 mL

7. The volume in liters/mole is 23.7 L/mol. This is 1.3 L greater than than the expected 22.4 L/mol.

23,702.8 mL=23.7 L/mol

8. The percent error between 23.7 L/mol and 22.4 L/mol is 5.5%.

22.4/23.7=0.945 1-0.945=0.055(100)=5.5%