IB INTERNAL ASSESMENT - CHEMISTRY LAB REPORT. Objective: I. Investigating the effect of pressure on the volume of gas. II. Investigating the effect of temperature on the volume of gas. III. Studying the ideal gas equation. Apparatus: Ruler, opened end monometer, glass tube, thermometer, conical flask, beaker, mercury plug, retort stand, Bunsen burner. Materials: Rubber band, aluminum foil, ice, water bath, anti bumping granule Experiment 1 - Boyle’s Law Hypothesis: The volume of gas is inversely proportional to its pressure. Variables: I. Independent: The gas pressure II. Dependent : reading of the ruler which represents the gas volume III. Constant: Temperature. Result: Reading on the clip: 47.30 ± 0.05 Reading where mercury of both opening has the same level: 34.00 ± 0.05 Volume of gas under atmospheric pressure Patm: 13.30 ± 0.05 Mercury Mercury Difference Pressure Height of Volume of PV level in level in in height = of gas, P gas ± 0.5 gas ± 0.5 closed opened P hg (P = Patm mm mm end end + P hg ) tube(mm) tube(mm) ± 0.5 mm ± 0.5 mm 100.0 163.00 63 196 238.0 238.0 46648 114.0 158.00 44 177 243.0 243.0 43011 117.0 147.00 30 163 248.0 248.0 40424 121.0 134.00 13 146 253.0 253.0 46938 144.0 132.00 12 145 258.0 258.0 37410 *Assuming that the diameter of the tube is constant, then the volume of the gas directly proportional to the height of gas column. Evaluation: The experiment shows the relationship between the pressure of the gas and its volume at constant temperature. According to Boyle’s Law, in a constant temperature, the volume of gas is inversely proportional to the applied pressure put on the gas. V ∝ 1/P V = k/P (k is a constant) VP = k
Theoretically, when graph PV against V (volume) is plotted we should get constant graph or one straight line stretches through the y- axis. Unfortunately, this kind of graph fails to be obtained due to some limitations. Experiment 2 - Charles’s Law. Hypothesis: The volume of gas is directly proportional to its temperature. Variables: I. Independent: The temperature of the environment II. Dependent :Volume of the gas III. Constant: Pressure of the gas. Result: Environment
Temperature of the water,(T ºC) ± 0.5 ºC
Warm water Pipe water Water + Icewater Water + Iceethanol
50.0 29.0 6.0
Temperature of the water in Kelvin (T) , T= T ºC + 273.15 323.15 302.15 279.5
-4.0
269.15
Height of the gas column ± 0.5 cm. 7.40 6.70 6.20 5.80
*Volume of gas. 7.40 6.70 6.20 5.80
*Assuming that the diameter of the tube is constant, then the volume of the gas directly proportional to the height of gas column.
Evaluation: The experiment shows the relationship between the temperature of the gas and its volume at constant pressure. According to Charles’s Law, at a constant pressure, the volume of gas is inversely proportional to the absolute temperature of the gas. V ∝T V = kT (k is a constant) V/T = k Theoretically, when graph Volume (V) against Absolute Temperature (K) is plotted we should get a liner graph with k (the constant) as a gradient of the graph. Unfortunately, this kind of graph fails to be obtained due to some limitations.
Experiment 3 - Ideal Gas Law Results: Mass of the conical flask + foil + rubber band: 67.8405 ± 0.0001g Mass of the conical flask + foil + rubber band + condensate: 67.9441 ± 0.0001g Mass of condensate: 0.1036 ± 0.0001g Temperature of the boiling water: 97.0 ± 0.5 ºC Barometer reading: Volume of the conical flask (represents the volume of the condensate): 155 ± 0.5 ml Based on Ideal gas equation: PV = nRT P= Pressure applied V= Volume of the gas T= Absolute Temperature n = number of mol R= Gas constant We know that, mass /relative molecular mass = number of mol m/M = n Hence, PV = nRT PV = m RT M M= m RT PV
In this case, R: 8.134JK-1mol-1 P: 733mm Hg X 101.325 kPa 760mm Hg =97.7253 kPa V: 155.0 cm3 1000 =0.155 dm3 T: 73.30 ºC + 273.15 =376.42 K Relative molecular mass of unknown compound can be determined using this formula, M= m RT PV =(0.1036 g)( 8.134JK-1mol-1)( 376.42 K) (97.7253 kPa)( 0.155 dm3) =20.9 gram mol-1
Limitations and recommendations: Limitations The clip that is clipping the tube might not be air thigh The ruler is not a perfect measurement instrument to measure the level of the mercury because it has large scales and uncertainties. The heat from our hand (generated by our body) might affect the results of the experiment when we hold the glass tube. When we took out the gas tube out of its environment to record the height of the gas column, the room temperature will affect the reading if we take too much time to determine the reading. The unequal distribution of heat wills influent the results.
Recommendations We can fold the tube several times and then clip it to ensure that it is air thigh Replace ruler with other measurement instrument that has smaller scales and smaller uncertainties Avoid holding the glass tube using our hand. After we took out the gas tube out of its environment, we need to take the reading as fast as possible to avoid the room temperature from influents the reading. We can stir the water slowly using a glass rod to distribute the heat in the water evenly.
Conclusion: The gas law is mathematically related to the temperature (T), pressure (P) and volume (V). The relationships are stated by Boyle’s Law, Charles Law and Ideal Gas Law.
Pressurer multiply by volume(PV)
Graph of PV againts V 50000 40000 30000 20000 10000 0 238
243
248
253
258
Volume(V)
Volume, V (cm)
Graph of Volume,(V) againts Absolute temperature,T(K) 8 6 4 2 0 269.15
279.5
302.15
Absolute temperature,T(K)
323.15
