Report -5- Gas Laws - general cgemistry lab 5-gas laws PDF

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general cgemistry lab 5-gas laws...

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Exploring the Properties of Gases

PROCEDURE: Procedure was followed as written. RESULTS Table 1: Pressure and Volume Volume (mL)

Pressure (kPa)

15

101.4 kPa

13

105.07 kPa

11

135.97 kPa

09

165.03 kPa

07

202.06 kPa

Figure 1: Relationship between Pressure and 1/Volume

Table 2: Pressure and Absolute Temperature

Temperature (K)

Pressure (kPa)

277.65

95.45

296.25

102.33

338.15

130.05

319.45

116.72

Temperature K = Temperature ºC + 273.15

Temperature K = 4.5 + 273.15 = 277.65 K

Figure 2: Relationship between Pressure and Temperature

Table 3: Volume and Absolute Temperature Total Volume (mL) (refer to step 7)

Temperature Range Actual (ºC) Temperature (ºC)

Pressure (kPa)

177

45-50

47.1

102.30

174

40-44

41.1

102.40

169

35-39

37.0

102.66

164

30-34

31.7

102.60

160

25-29

27.3

102.60

Total Volume = Volume flask + Volume Tubing + Volume syringe Volume flask = 140 mL Volume tubing = ~4 mL Volume flask+ Volume tubing = 144 mL Total Volume = 144 mL + 33 mL = 177 mL

Figure 3: Relationship between Volume and Temperature

Analysis of results: In Part I, two variables, volume (V) and pressure (P), were observed where n(molecules) and T(temperature) were constant. It was observed that the pressure increases as the volume decreases, so it shows the inverse proportion between them. Boyle’s law can be identified with these trends. In Part II, two variables, temperature(T) and pressure (P) were observed where n(molecules) and V(volume) were constant. It was observed that the pressure increases as the temperature increases, so it shows the direct proportion between them. Gay-Lussac’s law can be identified with these trends. In Part III, two variables, temperature(T) and volume (V), were observed where n(molecules) and P(pressure) were constant. It was observed that the temperature decreases as the volume decreases, so it shows the direct proportion between them. Charles’s law can be identified with these trends.

DISCUSSION 1. At constant temperature, if n represents the moles of gas present, what would be the expected relationship between pressure (P) and the number of moles of gas (n). (3 pts.) Hint: Assume that Avogadro’s hypothesis that “equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules” is true. As the number of moles of gas (n) increases, pressure (P) increases, so there is the direct proportion between them. (P α n) 2. Based on the relationship between P, T, n and V, state a combined gas law connecting all the four variables using a new proportionality constant, K. Justify your answer. (5 pts.) The combined gas law comprises of combining of Boyle’s Law, Charles’ Law, Gay-Lussac’s Law and Avogadro’s Law. PV = constant (n, T) Boyle’s Law P1 x V1 = P2 x V2 P α 1/V or P= constant (k) x 1/V or P x V= k VT = constant (n, P) Charles’ Law V1/T1 = V2/T2 V α T or V= constant (k) x T PT = constant (n, V) Gay-Lussac’s Law P1/T1 = P2/T2 P α T or P= constant (k) x T Vn = constant (P, T) Avogadro’s Law V1/n1 = V2/n2 V α n or V= constant (k) x n Then ideal gas law becomes PVnT = constant, in this case constant is R

R = 0.08206 Latm/molK P1 V1/ P2 V2 = n1T1/ n2T2 Merging these four laws produces the ideal gas law, a relation between the pressure, volume, temperature, and number of moles of a gas: PV=nRT 3. From your plot of pressure vs. temperature, why is the unit of temperature in the gas equation reported in Kelvin? What would happen if degrees Celsius were used? (5 pts.) The Celsius matrix is not an absolute matrix. The zero points are the freezing point of water at 0 ° C, not the lowest possible temperature. Negative temperatures are possible. When the temperature of a gas as Celsius doubles, the volume of the gas does not increase twice. But as Kelvin, the temperature doubles, and the volume increases twice. Kelvin chart is an absolute chart and 0 K is the lowest possible temperature. Neither negative length nor negative volume nor a negative absolute temperature. When the gases cool, they first liquefy, then solidify, but they cannot reach 0 K as gas. 0K is a utopian point where the volume of a gas is zero because on 0K point there is no energy in the matter. On the other hand, all the gas laws use equation and denominator is temperature, if we try to calculate 0 degrees it does not exist, so gas laws can’t work at that time. 4. Identify the three gas laws covered in this experiment. Describe the relationship observed in each law. Then, describe the relationship observed in the experiment. Do your findings support the gas laws? If not, explain why. (7 pts.) Hint: Review the gas laws table completed in the pre-lab activity. Boyle’s Law, Charles’ Law, and Gay- Lussac’s Law were covered in this experiment. Boyle’s Law was identified first part of the experiment, where volume and pressure observed when molecules and temperature are constant. According to Boyle’s Law, which relies on the

decrease of the volume as the pressure increases, it is observed that the pressure increases as the volume inside the syringe decreases. Gay-Lussac’s Law identified the second part of the experiment, where pressure and temperature observed when molecules and volume are constant. According to the Gay-Lussac’s Law, which is based on the direct proportion between temperature and pressure, it is observed that the temperature and pressure of the gas in the beaker increases as the temperature of the water in the container increases. Charles’s Law identified the last part of the experiment, where volume and temperature observed when molecules and pressure are constant. According to Charles’s Law, which is based on the correct proportion between temperature and volume, it was observed that the indicator of the syringe connected to the beaker changed as the temperature of the gas inside the beaker where the pressure was kept constant increased. That is, as the temperature increases, so do the volume. 5. In Part III, as you placed the apparatus in the warm water bath, you should have noticed the volume of air in the syringe increased. Explain what has happened to the gas. What variable should have remained constant? (5 pts.) When the apparatus is placed in the warm water, the gas inside the beaker starts to expand, and its pressure increases, so the syringe is activated due to this pressure and the total volume increases. The pressure remains constant with the increase in total volume.

REFLECTION In this experiment, the behavior of gases against temperature, pressure and volume changes were examined. Thus, the ideal gas and other gas laws (Boyle, Charles, and GayLussac) were observed in the laboratory environment.

The experiment was started in Part III. After all the apparatus was checked and placed, the values taken were recorded. The attachment and control of the apparatus were done by me, ice was added by my friends to change the water temperature. Meanwhile, the values on the screen were followed by my teammates and recorded by another teammate. In this section, the first operations were repeated as a result of the error made by removing the apparatus from the water, and then the experiment was continued. The experiment continued with Part II. The apparatus was checked and placed by me and adding hot water and changing water inside the container were done by me. The values were recorded by my teammates. Finally, Part I was done by me and my teammates. Since the temperature of the gas inside the beaker changes with the cabin temperature in which the beaker is located, the temperature balance of the apparatus and water used should be adjusted well. Otherwise, the measured values may not give correct results. If the control of the apparatus used is not done well, the gas inside will come out, or the gas will be trapped inside. Therefore, the obtained results will be wrong....