EP103 FOUNDATION IN CHEMISTRY II LABORATORY REPORT
EXPERIMENT 1 BOYLE’S LAW
ANDREW ARVIND A/L SIMON (GROUP NO. 6) 1001231972
SCHOOL OF ENGINEERING FACULTY OF ENGINEERING, ARCHITECTURE AND BUILT ENVIRONMENT
SEPTEMBER 12, 2013
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TABLE OF CONTENT
Content
Page No
Objectives
3
Introduction
3-4
Materials / Apparatus
4
Results and Discussion
4-6
Conclusion
6
Limitation of experiment / Safety precautions
6
References
6-7
Appendix – Authenticated results
8
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Experiment 1 : Boyle’s Law
Objective
To determine the relationship between pressure and volume of an ideal gas.
To compare the experimental results with theoretical results.
Introduction
Boyle’s Law is an example of a limiting law, a law that is strictly true to a certain limit. Boyle's Law is a principle that describes the relationship between the pressure and volume of a gas. According to this law, the pressure exerted by a gas held at a constant temperature varies inversely with the volume of the gas. For example, if the volume is halved, the pressure is doubled, and if the volume is doubled, the pressure is halved. The reason for this effect is that a gas is made up of loosely spaced molecules moving at random. If a gas is compressed in a container, these molecules are pushed together thus, the gas occupies less volume. The molecules, having less space in which to move, hit the walls of the container more frequently and thus exert an increased pressure.
Boyle’s law states that at constant temperature for a fixed mass, the absolute pressure and the volume of a gas are inversely proportional. Forcing the volume V of the fixed quantity of gas to increase, keeping the gas at the initially measured temperature, the pressure P must decrease proportionally. Conversely, reducing the volume of the gas increases the pressure. The law can also be stated in a slightly different manner, that the product of absolute pressure and volume is always constant. The law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The before and after volumes and pressures of the fixed amount of gas, where the before and after temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
P1V1 = P2V2 (P = Pressure, V = Volume)
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In this experiment, Boyle’s Law is investigated and proven as well. A compressive pressure chamber will be used to compress and release the pressure as well. The pressures will be noted until they stabilize. The pressure will be recorded when the chamber is pressurized as well as when the pressure is released to vacuum at 1 bar as well as 2 bar pressure level.
Materials / Apparatus
Vacuum chamber
Pressure chamber
Air compressor
Methodology
1. The general start up procedures were performed as stated in appendix A. All the valves were made sure to be closed. 2. The compressive pump was switched on and the pressure inside the chamber was allowed to increase up to about 150kPa. Then, the pump was switched off and the hose was removed from the chamber. 3. The pressure reading inside the chamber was monitored until it stabilized. 4. The pressure reading for both chambers before expansion was recorded. 5. V 02 was fully opened and the pressurized air was allowed to flow into the atmospheric chamber. 6. The pressure reading for both chambers were recorded after expansion. 7. The PV was calculated and Boyle’s Law was proven.
Results and Discussion
o
Pressure , kPa
Temperature, C
No
Chamber
P1
P2
T1
T2
1
Pressure
149.1
132.3
24.2
22.5
2
Vacuum
101.2
134.5
20.9
21.6
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According to Boyle’s Law, P1V1 = P2V2
Pressure Chamber = 25 L Vacuum Chamber = 12.2 L
(P1V1 + P2V2) before expansion = (P1V1 + P2V2) after expansion (149.1)(25) + (101.2)(12.2) = (132.3)(25) + (134.5)(12.2) 3727.5 + 1234.64 = 3307.5 + 1640.9 4962.14 = 4984.4
Percentage error :
=
x 100%
= 0.276 %
Boyle’s Law states that for a fixed mass of gas at constant temperature, the volume is inversely proportional to the pressure. Pressure is caused by gas molecules hitting the walls of the container. With a smaller volume, the gas molecules will hit the walls more frequently, and so the pressure increases. If the pressure of a fixed mass of gas is increased without changing the temperature, the only way you can do it is to squeeze it into a smaller volume. That causes the molecules to hit the walls more often, and so the pressure increases. If the volume of the container is reduced, the gas molecules have a shorter distance to travel before they collide with the walls of the container. This means that they collide with the walls more frequently. The change of momentum that takes place at the surface of the walls occurs in a shorter time, resulting in a greater force exerted by the molecules on the walls, and hence a greater pressure.
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Boyle’s Law applies to all gases regardless of its chemical identity (provided that the pressure is low) because at low pressures, the average separation of molecules is so great that they exert no influence on one another and hence travel independently. The kinetic energy of the particles is proportional to the temperature. The compression will be isothermic in nature. All the external energy is transferred indirectly to the environment since the gas remains at its temperature when the compression is extremely slow. At constant temperature if volume of a gas is reduced, gas molecules will come close to each other but there is no change in the velocity of gas molecules.
The pressure does not equal theoretically. The difference in pressure may have been due the pressure that escaped during the expansion. This causes an inaccurate result and a slight percentage error of 0.276%.
Conclusion
The pressure increases when the volume decreases in both the chambers which undergoes expansion and hence Boyle’s Law is proven.
Limitation of Experiment
The pump pressure is set the maximum to level 2 as excess pressure may result in the breaking of the glass.
The valves were closed tightly each time to avoid movable pressure from each chamber into one another.
The volume may not always be constant as it may vary.
References
Website
David N.Blauch (2009, June). Gas Laws : Boyle’s Law. Retrieved on September 14, 2013, from http://www.chm.davidson.edu/vce/gaslaws/boyleslaw.html.
Kent Krinnasch (2007, May). Boyle’s Law. Retrieved on September 14, 2013, from http://www.kentchemistry.com/links/GasLaws/Boyles.htm.
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Cliff Notes (2007). Boyle’s Law. Retrieved on September 15, 2013, from http://www.cliffsnotes.com/sciences/chemistry/chemistry/gases/boyles-law.
Reference Book
Peter Atkins and Julio De Paulo (2010). Physical Chemistry. (9th edition). W.H. Freeman and Company.
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