P-V Relationships for a Gas and Determination of R PDF

Preview

Summary

small lab report...

Description

TECHNICAL MEMORANDUM DATE: April 14, 2019 RE: P-V Relationships for a Gas and Determination of R Devices used: buret

leveling bulb

v-tube connectors

balance beam rubber tube clamp

pinch clamp

Raw Data: Section A: Determining the PV functional relationship Uncalibrated volume, Vu (mL)

3.3 5

Temperature of water, T (°C)

24. 4

Barometric Pressure, Patm (atm)

754

Height difference between water levels, h± (mm)

Volume of air (mL)

(-) 444.5

27.1

(+) 772.16

23.5

0

25.52

Section B: Determination of R Mass of tube plus KClO3 (g)

6.408

Mass of tube plus residue after heating (g)

6.358

Initial gas level in buret (mL)

0

Final gas level in buret (mL)

38.7

Barometric pressure (mm Hg)

754

CHEM 1100

MJH-Fall 2018

Page 1

23.35

Room temperature (°C)

Key Results: Section A: Determining the PV functional relationship Vapor pressure, PH2O (mm Hg): 22.4 mm Hg Height difference between water levels, h± (mm)

Pcolumn (atm)

Pair (atm)

Vair (mL)

PV (mL. atm)

h0

0

0

731.4=0.96236856

28.87

27.7835803272 mL.atm

h1

-444.5

-32.68=-0.043000006

698.92=0.919500131

30.45

27.998778989 mL. atm

h2

772.16

56.78=0.074710537

788.38=1.03773699

26.85

27.863281815 mL.atm

h3 h4

Section B: Determination of R Number of moles of oxygen (mole)

0.0015625 mole

Pressure of oxygen (atm)

0.963 atm

Volume of oxygen (L)

0.0387 L

Ideal gas constant, R (L. atm/mol. K)

CHEM 1100

0.8048450 L.atm/mol.K

MJH-Fall 2018

Page 2

Sample Calculations: Part A:

Pcolumn =h(mm)×

d❑H 2 O 1.00 =−444.5mm ( )mmHg=−32.68 mmHg=− 0.043000006 atm 13.6 d gas

Pair =Patm + Pcolumn−P H O=754 mmHg+(−32.68 )−22.4 mmHg=698.92 mmHg=0.919500131 atm 2

V air =V reading +V u=27.1 + 3.34 =30.45 mL PV =Pair × V air =0.919500131 atm ×30.45 mL=27.998778989 mL. atm Part B:

number of moles=n=

pressure of O2=P= volume of O2 =V =

mas s initial−mas s final 6.408 g−6.358 g 0.05 g = = =0.0015625 mol molar mass of O2 32.0 g /mol 32.0 g /mol

barometric pressure−vapor pressure H 2 O 754 mmHg−22.4 mmHg = =0.963 atm 760 mmHg/atm 760 mmHg/atm

38.7 mL =0.0387 L 1000 mL/ L

temperature of O 2=T =room temperature+273=296.35 K

constant R=

atm . L 0.963 atm × 0.0387 L P ×V =0.8048450 = mol . K n ×T 0.0015625 mol ×296.35 K

Interpretation of Key Results:

What was the aim of this experiment? The aim of this lab is to determine the value of R by using a manometer to find pressure, measure volume, and

absolute temperature of two different gases. In order to weigh the number of moles, it can be determined by using two methods: with weighing and by the reaction of stoichiometry. What is the water manometer? What is the difference between this manometer and a barometer? Explain. By deifinition a manometer is a pressure device made of a U-shaped glass and it is used to measure the differences in pressure with balancing the weigh of fluid between two different pressures in the U-shaped glass. A barometer is a device that measures the pressure at a certain level, while a manometer measures the difference of two air pressures inside different systems. What is the use of Dalton’s partial pressure law in a water manometer? In which equation in your manual this law has been used? Write the equation and define its terms. CHEM 1100

MJH-Fall 2018

Page 3

Pair = Patm + Pcolumn−P H

Equation

2

O

uses the Dalton’s partial pressure law. P atm represents pressure of the room ,

Pcolumn represent the pressure exerted by the differences in wate levels , and P H2O represents the water vapor pressure at a certain temperature. The use of Dalton’s partail pressure law in a water manometer is finding the different pressures (P) of different levels of water differences using a water manometer since it displaces two systems at the same time.

Write a formula to present the pressure of air, Pair , when the level of the water in the bulb and in the buret is the same. Explain reasoning of your answer.

Pair+ PH O=P atm + Pcolumn can the formula that represents when the level of the water in the bulb and in the buret is 2

the same because Pair and PH2O represent the water levels of the bulb while Patm and Pcolumn represent the water levels in the buret, them being equal to each other means that their water levels are the same. If the decomposition of potassium chlorate is not complete and you stop collecting oxygen how would affect the accuracy of R? Write the balanced decomposition reaction for potassium chlorate and prove your answer by using the ideal gas law expression.

2 KCl O3 (s)→2 KCl(s)+3O 2 It would affect the accuracy of R since the volume, pressure , and number of moles of O2 is needed to calculate constant R. On the equation it shows that in the complete decomposition of potassium chlorat there are three moles of O2, that could be different if all the oxygen is not collected during the reation. The volume of oxygen and the pressure of oxygen will be different depending on the amount of oxygen collected, leading to also changing the R constant during calculations. How would the following affect your results (Qualitatively): (a) A drop of liquid water is present in the air column in Part B before the volume of oxygen is read. If drop of water is present in Part on the air column, we would need to caliberate the device again to avoid any systematic error during the collection of data and during the calculations. (b) A slow leak of air takes place from the gas measuring tube in Part A. If there is a slow leak of air in the gas measuring tube in Part A, the water in the tube would no be able to level with buret or stop rising when moving the tube up or down, the data collected would be off. The leak of air would need to be fix to have leak prood tubes in order for the set up to work as its supposed to. ( c) The hard glass tube is not allowed to cool in Part B. If the hard glass tube is not allowed to cool in Part B after heating, the mass of the glass tube after heating would not be the appropriate amount of mass and would give us a different mass than when it is allowed to cool down.

Calculate the uncertainty in the value of R that you found in this experiment. Does your value agree with the literature value within experimental uncertainty? What is the measurement that gives rise to the most uncertainty in your result.

Comment on any other interesting facts or interpretations.

CHEM 1100

MJH-Fall 2018

Page 4

References 1. Goldwhite, H., Tikkanen, W., Kubo-Anderson, V., & Mathias, E. (n.d.). Experiments in General Chemistry(5th ed.). Macmillan Learning, 2018. p.27-33.

Figures: Figure 1.

Figure 2.

CHEM 1100

MJH-Fall 2018

Page 5

Figure 3.

CHEM 1100

MJH-Fall 2018

Page 6...