Determination of Gas Constant R
Student name: Peter S. Byun
Course; IB Chemistry SL1
The purpose of this experiment is to use a eudiometer to determine experimentally the gas constant value R.
Data Collection and Processing:
Table1: Quantitative Data collected throughout the experiment.
| Trial 1 | Trial 2 | Trial 3 |
Mass of magnesium/g (±0.005) | 0.03 | 0.03 | 0.03 |
Water depth/mm (±0.1) | 70 | 70 | 70 |
Volume of H2 gas collected/L (±0.00005) | 0.0254 | 0.0506 | 0.0514 |
Pressure of water liquid/kPa (±0.5) | 0.686 | 0.686 | 0.686 |
Pressure of water vapor/kPa | 3.2 | 3.2 | 3.2 |
Pressure of hydrogen gas dry/kPa (±0.5) | 98.8 | 98.8 | 98.8 |
Room temperature/℃ (±0.05) | 23.9 | 23.9 | 23.9 |
Constant R/LkPaK-1mol-1 | 8.312381 | 8.313808 | 8.312476 |
Percent Error/ % | 0.02515 | 0.00799 | 0.02401 |
Qualitative Data collected throughout experiment
1. When the eudiometer was reversed and fixed onto the ring stand, hydrochloric acid slowly descended and mixed with the deionized water.
2. As the magnesium ribbon reacted with HCl, tiny bubbles formed around the copper tied around the magnesium.
3. As the reaction proceeded, the bubbles grew bigger and floated upward.
Introduction: In this experiment, the problem trying to be solved is what gas laws are being used when the pressure, temperature, and volume are being measured. The three gas laws are Boyle’s Law, Charle’s Law, and Gay-Lussac’s Law. The Boyle’s Law is when volume and pressure are being compared. Pressure and volume are inversely proportional, because when pressure goes up, volume goes down. The ...
4. The reaction happened even faster and more rigorously as it reached the climax. Bubbles formed one after another and shot upward in a zigzag motion.
5. While the reaction happened, MgCl2 was created and flowed downward. This then sank to the bottom of the beaker. The seemingly oily substance was not soluble, for difference between the substance and deionized water was visually comparable.
6. The formation of bubbles suddenly reduced in size and amount and when almost all of the reaction lessened.
7. Even after the complete dissolution of the magnesium ribbon, the colorless substance continued to move around the burette, and flowed out of the burette into the beaker.
8. Miniscule bubbles stuck to the copper either floated upwards.
1] Mass of magnesium
Using the fact that one mole of gas occupies 22.4L at STP, calculate the amount of Mg metal that will produce 30 and 40 mL of H2 gas.
∴ We can use between 0.0326g and 0.0434g Mg. In this experiment 0.03g±0.005 magnesium is used.
2] Calculating the pressure of water liquid (PH2O(l)) from water depth
Water depth= 70±0.1 mm
∴ The pressure of water liquid (PH2O(l)) is 0.686kPa±0.1
3] Pressure of water vapor (PH2O(g)) from the reference(1)
At this temperature PH2O(g) is 3.2kPa±0.05
4] Calculate the Pressure of hydrogen gas (PH2(g)) dry using Dalton’s law
Patm = Phygrogen gas dry + Pwatervapor + Pwater liquid
Phydrogen gas dry = Patm – Pwater vapor – Pwater liquid
Patm = 102.7kPa from the reference at 1PM on Oct. 18, 2011 at Suwon observation center(2)
Phydrogen gas dry = (102.7±0.05)-(3.2±0.05)-(0.686±0.1)
∴ Phydrogen gas dry =98.815kPa±0.2 =98.8kPa±0.2
Experiment 3: Evaluation of Gas Constant Purpose: The purpose of this lab is to demonstrate the ideal gas law under ordinary conditions. In this lab, the variables in the ideal gas law are known or can be found aside from the constant R. Thus, the R values can be found and relatively determine the relevancy of the ideal gas law to the lab conditions. The ideal gas law was tested using the ...
5] Estimate volume of H2(g) (VH2) at STP using combined gas law
* Estimating uncertainty
∴ Volume of the hydrogen gas at STP (VH2) is 0.0227558L±0.0000075≒0.02276±0.0000075.
6] Calculate the number of moles of H2
7] Calculate gas constant R
8] Percentage error
Actual value of gas constant, R=8.314472kPaLmol-1K-1 (3)
% Error=Experimental value-Actual valueActual value×100%
Conclusions and Evaluation:
The gas constant is a physical constant that features in a number of fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation. It is in units of energy per kelvin per mole. It is equivalent to the Boltzmann constant, except that the latter is expressed in units of energy per kelvin per particle.(3)
Gas constant value R is experimentally determined by using eudiometer. R values from three trials are 8.312381, 8.313808, and 8.312476 L∙KPa/mol∙K with uncertainty less than ±0.03, respectively. Average R value from the experiment was 8.312888 L∙KPa/mol∙K. Actual gas constant value is 8.314472 L∙KPa/mol∙K. Percentage errors are 0.02515%, 0.00799%, and 0.02401%. Results for this experiment are accurate and precise.(3)
Even with such precise data, it is undeniable that limitations exist and systematic errors occurred during the experiment. First, the biggest error could have been us reading the volume of hydrogen gas slightly off. A slight misreading could lead us to a very wrong calculation later on. Secondly, the measurement of our limiting reagent, magnesium, could have been off. During the experiment, we used digital scales, which were not very accurate. They had an uncertainty value of ±0.005, which could have easily changed the amount of MgCl2 produced during the experiment for each trial. Lastly, a minor effect that could have caused the errors might have been the location of where the experiment took place. Some ways to improve on reducing the errors could be to bring your eye level to the height of the water level at the high point and at the low point because observing both points at just one level will likely create errors to both observations. Another way to improve could be to use more accurate scales with more decimal points available rather than digital scales with only up to two decimal points. The third way of improving could be to measure the pressure of laboratory during the time of experiment and use that number in the calculations.
A gas is the state of matter that is characterized by having neither a fixed shape nor a fixed volume. Gases exert pressure, are compressible, have low densities and diffuse rapidly when mixed with other gases. On a microscopic level, the molecules (or atoms) in a gas are separated by large distances and are in constant, random motion. When dealing with gases, the Ideal Gas Law equation is the ...
* 1] “Vapour pressure of water – Wikipedia, the free encyclopedia.” Wikipedia, the free encyclopedia. N.p., n.d. Web. 26 Oct. 2011. <http://en.wikipedia.org/wiki/Vapour_pressure_of_water>.
* 2] “도시별 현재날씨 > 지상관측자료 > 관측자료 > 날씨 > 기상청 .” ’하늘을 친구처럼, 국민을 하늘처럼’ :: 기상청. N.p., n.d. Web. 26 Oct. 2011. <http://www.kma.go.kr/weather/observation/currentweather.jsp?auto_man=m&type=t99&tm=2011.10.18.13%3A00&x=28&y=10>.
* 3] “Gas constant – Wikipedia, the free encyclopedia.” Wikipedia, the free encyclopedia. N.p., n.d. Web. 26 Oct. 2011. <http://en.wikipedia.org/wiki/Gas_constant>.