Lab Report Gas Laws

Understanding Gas Laws CHEM 1007 Spring 2015

This report shows a working knowledge of lab #4 “Gas Wars” in chemistry lab 1 at the University of New Orleans. I certify that all works within are original and that the bounds of the experiment derive from the class’s corresponding workbook. Sam Sternfield

Understanding Gas Laws: INTRODUCTION: In this experiment, the goal is to analyze the behavior of gaseous compounds under varying conditions in order to see a change in the gas’s properties. The ideal gas law will be used in order to determine the mathematical relationship between different properties. The ideal gas law can be represented with the formula PV=nRT. According to Boyle’s law (P1/V2 = P2/V1) and Charles’s law (V1/T1=V2/T2), we can show a relationship between pressure and volume, as well as the volume and temperature of a gas. As these constants are manipulated, a change in the other variables will be noticed in the gas. If the pressure of a gas is manipulated at constant temperature, then the volume of the gas will change in an inverse relationship. If the temperature of a gas is manipulated at constant pressure, then the volume of the gas will change in the same way.

EXPERIMENTAL: In the experiment, two different tests were conducted in order to see if there is a relationship between pressure and volume as well as volume and temperature. In order to test pressure versus volume, a known volume of oxygen in a sealed syringe and different pressure were applied to the syringe. The pressure was manipulated by adding weight to the top of the syringe.

The result would be a change in volume. A relationship between pressure and volume can be determined because the amount of weight can be used to calculate pressure with the formula P=F/A and F = mg.

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In order to test volume versus temperature, an oil bath will be used to heat up a gas at constant pressure. The oil will be measured in length to determine the volume of the gas. As the measuring device is removed from the oil bath, the temperature will decrease and therefore the length of oil in the sensor will decrease in accordance with the volume of the substance.

The result of changing the temperature of the substance will cause a change in the length of oil in the tube. A relationship between temperature and volume can be deduced because volume can be calculated by using the formula V=L A where L is the length of the tube and A is the area of the tube (Essentially the formula used to calculate the volume of a cylinder). DATA: *Volumes and Masses Recorded to Demonstrate Pressure V.S. Volume Mass (lbs) 0.0

Mass Volume (+/- . Force Pressure (g) 5mL) (N) (kPa) 0 53 n/a n/a 1133.9 2.5 8 47 11 23 2267.9 5.0 6 39 22 45 3401.9 7.5 4 34 33 68 4535.9 10.0 2 30 44 91 *Procedure was replicated multiple times with no change in results*

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Force and Pressure at 2.5lbs against the system calculations: 2.5lbs X 453.592g/lbs X 1kg/1000g = 1.13398kg Force = mg F = 1.13398kg X 9.81 m/s2 F = 11.1243438N Pressure = F/A   r = 12.5mm r = 12.5mm X 1m/1000mm r = .0125m P = 11.1243438N / [ (.0125m)2] P = 2.3 X 104 Pa X 1kPa/1000Pa P = 23 kPa Temperature and Length of Oil in Tube Used to Demonstrate Temperature V.S. Volume Temperature (+/- . Length of Oil (+/- . Volume of Oil 1°C) 1mm) (mm3) 80.4 8.0 7.6 75.3 7.0 6.7 61.2 6.0 5.7 82.1 6.2 5.9 70.7 5.3 5.0 64.4 4.5 4.3 51.3 3.2 3.0 82.4 6.0 5.7 67.7 5.1 4.8 Page 3 of 7

57.2 50.1 85.4 77.8 69.4 61.7

4.2 3.7 6.9 6.0 5.0 4.1

4.0 3.5 6.6 5.7 4.8 3.9

Volume of Oil at 80.4°C: Volume = L * V = 8.0mm ( ) (.55mm)2 V = 7.60mm3

RESULTS: In the first experiment demonstrating pressure’s effect on volume, the pressure changes from 23 to 91kPa. As the pressure increases across this range, a decrease in the volume of the gas in the syringe is expected to decrease. This does correlate with the data and Boyle’s Law because as the pressure increases along this range, volume decreases from 47 to 30mL. Possible sources of error include the inaccuracies in reading the volume in the syringe and getting all of the weight to be applied directly to the syringe. Efforts in the second experiment to show temperature’s effect on volume, temperature readings range from 50.1 to 85.4°C. As the temperature decreases along this range while the substance is removed from the oil bath, a decrease in the Page 4 of 7

length of oil in the tube is expected to increase. An decrease in the length of the oil would reflect a decrease in the volume of the substance. This expectation is met and correlates with Charles’s Law. As the temperature decreased in the experiment, the length of oil did decrease from 8.0 to 3.2mm. Sources of error include misreading the temperature due to either lack of human response time or reading the sensor before the actual temperature at the given moment was detected. CONCLUSIONS: The data shows an inverse relationship between pressure and volume. As pressure increases at constant temperature, volume will decrease by the same factor. This correlates to Boyle’s law. This is seen in the data because as weight is added to the system, the pressure increases. As more weight is added, the volume of the gas decreases. The data additionally shows a proportional relationship between temperature and volume. This does correlate with Charles’s Law. This is seen in the data because as the temperature decreases when the sensor is taken out of the oil bath, the length of the oil in the sensor decreases. When the length decreases, volume decreases according the formula indicated. Therefore as temperature decreases, the length of oil in the sensor decreases. The combined gas law is synthetic formula based on the ideal gas law PV=nRT, as well as Boyle’s Law and Charles’s Law. When the same number of gaseous moles is being examined in a system there is a relationship between pressure, volume, and temperature. P1V1=nRT1 after some change in the system: P2V2=nRT2 Therefore the combined gas law can be reduced as: P1V1/T1 = P2V2/T2 As more complete combined gas law can be used with the inclusion of moles. This would be: P1V1/n1T1 = P2V2/n2T2 The data did match the hypothesis as the relationships between pressure and volume as well as temperature and volume did match the corresponding mathematics associated with the respective gas laws. For example, while demonstrating Boyle’s law and the weight increased from 2.5 to 5.0 pounds, the pressure increased, and the volume of the gas in the syringe decreased. This shows the inverse relationship between pressure and volume of a gas. REFERENCES:

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Tarr, M.A., CHEM 1007 – GENREAL CHEMISTRY LAB 1 DEPARTMENT OF CHEMISTRY UNIVERSITY OF NEW ORLEANS; University of New Orleans: New Orleans, 2010

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