Name ______& ______Period ______
Determination of the Universal Gas Constant (R)
INTRODUCTION:
The ideal gas law was determined by measuring a series of gasses (1mol of them) at the same pressure temperature and volume. It was found that no matter what the gas was, when you divide the product of the pressure and volume by the product of the number of moles of gas there where wand the temperature you always get the same number,
R = 0.0821 or
This constant number R was called the universal gas constant applies to all gasses. However, because the units for P,V, N, and T can change R is unit specific. In order to use 0.0821 as R you must have the following units:
P = atm
V =L
n = number of moles
T = Kelven
In this lab you will react a piece of Mg metal with hydrochloric acid and capture the H2 gas that is produced. By using stoichiometry to calculate the number of moles of gas produced, as well as measuring the pressure, temperature and volume of gas produced you will hopefully be able to mathematically determine R from your measurements.
Before You Begin:
- What will you be doing in this lab?
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- What is the goal of this lab?
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- How will measure the P, V, N, and T of the H2 gas produced in this lab and what units will you need to measure them in?
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Procedure:
1. Record the mass of piece of magnesium ribbon approximately 2.5 cm in length.
2. Coil the ribbon. Cut and wrap a piece of copper wire (15 cm) to form a “cage” around the magnesium. Thread one end of the copper wire through the hole in the rubber stopper.
3. Fill a battery jar or large beaker about 2/3 full of water.
4. Pour 10 mL of 6.0M HCl into the gas measuring tube.
5. Slowly pour water into the tube without mixing it with the acid. Fill it to the very top.
6. Place the stopper with the magnesium in the copper cage into the eudiometer tube so that the magnesium ribbon is inside the tube.
7. Place your thumb over the hole in the stopper and invert the tube into the battery jar. Clamp the tube to a ringstand.
8. When the reaction stops, adjust the tube so that the water level in the tube is the same as the level in the battery jar. Add water to the battery jar if necessary.
9. Record the volume, temperature of the water (assume this to be the gas temp) and the barometric pressure.
10. Repeat the procedure for a second trial if there is time.
Data Table:
1. Write the complete balanced equation for the reaction that occurred below.
Trial 1 Trial 2
2. Mass of Mg______
3. Moles of H2 produced ______
(show stoichiometric calculation)
4. Volume of H2 in milliliters______
5. Volume of H2 in liters______
6. Barometric Pressure (total pressure in the tube)______
7. Temperature of water (and gas)______
8. Vapor Pressure of water at indicated temperature______
9. Partial pressure of H2 in mmHg______
10. Partial pressure of H2 in atm______
11. Value of R (show calculation below)______
12. Accepted value of R 0 .0821 L.atm/K.mole
14. Percent Error______
Vapor Pressure of Water from 0oC to 100oCT (oC) / P (mm Hg) / T (oC) / P (mm Hg) / T (oC) / P (mm Hg)
0 / 4.6 / 26 / 25.2 / 16 / 13.6
1 / 4.9 / 27 / 26.7 / 17 / 14.5
2 / 5.3 / 28 / 28.4 / 18 / 15.5
3 / 5.7 / 29 / 30.0 / 19 / 16.5
4 / 6.1 / 30 / 31.8 / 20 / 17.5
5 / 6.5 / 31 / 33.7 / 21 / 18.7
6 / 7.0 / 32 / 35.7 / 22 / 19.8
7 / 7.5 / 33 / 37.7 / 23 / 21.1
8 / 8.1 / 34 / 39.9 / 24 / 22.4
9 / 8.6 / 35 / 42.2 / 25 / 23.8
10 / 9.2 / 36 / 44.6 / 42 / 61.5
11 / 9.8 / 37 / 47.1 / 43 / 64.8
12 / 10.5 / 38 / 49.7 / 44 / 68.3
13 / 11.2 / 39 / 52.4 / 45 / 71.9
14 / 12.0 / 40 / 55.3 / 46 / 75.7
15 / 12.8 / 41 / 58.3 / 47 / 79.6
Abstract:
\(Note: Don’t use first person. Abstract should say:
What you did,
Why you did it,
How you got your conclusions,
What your conclusions where
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