...I missed the class prior to this lab and I am completely lost, please expain
ID: 3697737 • Letter: #
Question
...I missed the class prior to this lab and I am completely lost, please expain your solutions. Thank you. all questions are at the bottom of the page. :)
Experiment 11: Gas Laws
I. INTRODUCTION
Gases are made up of molecules that are in constant motion and exert pressure when they collide with the walls of their container. The number of collisions the molecules will have is affected by temperature and volume. In this laboratory, you will explore how the pressure of a gas depends on changes in volume and changes in temperature.
II. BEFORE YOU COME TO LAB
1. Read the entire lab. 2. Review sections 10.2 – 10.3 in your text on Gas laws. 3. Complete the pre-lab assignment on the course website.
III.PRESSURE/VOLUME RELATIONSHIP: BOYLE’S LAW
Obtain and wear goggles!
Equipment you will need:
LabPro kit Pressure Sensor kit A. Connect the Gas Pressure Sensor from the gas pressure sensor kit to CH1 of the LabPro. Make sure the USB cable connects the LabPro to the computer and that the LabPro is plugged into the outlet. Make sure everything is connected before you open the
computer program.
B. Open the desktop folder entitled “Student Work Files” and then the “Chemistry 121” folder. Double click on the file “Expt 11 Boyle’s Law” to open the LoggerPro program.
C. The computer should open a graph window showing the independent variable as volume and the dependent variable as pressure. If your LabPro is properly connected, you should see a green “Collect” button at the top of the screen. D. Take the syringe from the Pressure Sensor kit and set the piston of the syringe with the front edge of the inside black ring (indicated by an arrow in Figure 1) at the 10.0 mL mark.
Figure 1
100
E. Attach the syringe to the valve of the Pressure Sensor as shown in Figure 1. Do not disconnect the syringe until you are completely done collecting your data. F. Click the green “Collect” button to begin data collection. When the pressure reading in the window in the lower left-hand corner of the screen stabilizes, click the “Keep” button to save the data. You will be asked to enter a volume. In order to accurately account for all of the gas in the syringe and in the pressure sensor, you will need to add 0.8 mL to the 10.0 mL you’ve set on the syringe. In other words, your first entry for volume should be 10.8 mL. Click “OK” when you have entered the volume. G. Move the syringe to the 5.0 mL position. Again, when the pressure reading has stabilized, click “Keep” to save the data and enter the syringe volume + 0.8 mL (in this case 5.8 mL). H. Repeat the process in Step G until you have collected data for syringe volumes of 7.0, 9.0, 11.0, 13.0, 15.0, 17.0, and 19.0 mL. I. Click the red “Stop” button when you have finished collecting all your data. J. In Data Sheet 1, record the pressure and volume data pairs displayed in the “Data Set” window on the computer. Do not fill in the Constant, k, column at this time.
...I missed the class prior to this lab and I am completely lost, please expain your solutions. Thank you.
DATA SHEET 1
Volume(mL)
Pressure(kPa)
Constant, k(P / V or P • V)
K. From the “Analyze” menu, select “Autoscale” to rescale your data points. L. Examine your data and see if the points appear to be in a straight line. 1. If your data appears to display a linear relationship (meaning you have a direct relationship), go to the “Analyze” menu and select “Linear Fit” to get the best-fit
linear regression. 2. If your data does not appear to display a linear relationship (meaning you have an inverse relationship), you will need to graph the data in a different way. a. From the “Data” menu select “New Calculated Column.” Enter “1/Volume” as
the Name, “1/V” as the shortname, and “1/mL” as the unit. b. In the “Expression” box type “1/” then select “Volume” from the “Variables (Columns)” list. In the “Expression” box, you should see displayed 1/”Volume”. Click “Done” when you are ready. c. On the graph, click on the independent variable axis name and select
“1/Volume” to be displayed on the x-axis.
d. In the “Analyze” menu, select “Autoscale” to rescale your data to fit the window. e. If the relationship now appears to be linear, go to the “Analyze” menu and select
“Linear Fit” to create a best-fit linear regression.
M. Once you have a linear regression fit completed, print out copies of the graph for you and your lab partner by going to the “File” menu and selecting “Print Graph.” Be sure to include a copy of the graph when you turn in your lab. N. Using the information from your graph, write an algebraic equation that expresses the relationship between the two measured variables. Remember to follow the format for this equation as illustrated on page 11. Be sure to use the names of the variables and correct units for the variables, slope, and intercept.
O. Discuss the quality (precision) of your data by providing specific references to your graph. P. Using your algebraic equation, calculate the pressure for the following volumes. Show your calculations. 25.0 mL: 50.0 mL: 100.0 mL: Q. What happens to the pressure if the volume is doubled from 50.0 mL to 100.0 mL? R. What happens to the pressure if the volume is cut in half from 50.0 mL to 25.0 mL?
S. What experimental factors are assumed to be held constant in this experiment? T. Since Boyle’s law states that the relationship between pressure and volume is a constant, determine the value of the constant, k. To do this, go back to how you made your graph—did you determine the original relationship between pressure and volume was direct or inverse? If the relationship was direct, then calculate k = P/V. If the relationship was inverse, then calculate k = PV. Record the values and units for each of your data points in Data Sheet 1.
How constant were the values for k that you obtained? Good data may show some minor variation, but the values for k should be relatively constant.
U. When you are done with this section, close the LoggerPro program, but keep your equipment as you will need most of it for the next section.
IV.PRESSURE/TEMPERATURE RELATIONSHIP: GUY-LUSSAC’S LAW
Equipment you will need:
LabPro kit Pressure Sensor kit Stainless steel temperature probe 125-mL Erlenmeyer flask
A. Connect the Gas Pressure Sensor from the gas pressure sensor kit to CH1 of the LabPro. Connect the Temperature probe into CH2 of the LabPro. Make sure the USB cable still connects the LabPro to the computer and that the LabPro is plugged into the outlet. Make sure everything is connected before you open the computer program.
B. Open the desktop folder entitled “Student Work Files” and then the “Chemistry 121” folder. Double click on the “Expt 11 Guy-Lussac’s Law.cmbl” to open the LoggerPro
program.
C. From the Pressure Sensor kit, obtain a stopper assembly like that shown in Figure 2. With the assembly open, place the stopper into the 125-mL Erlenmeyer flask and make sure the stopper is secure. If the fit is not good, then obtain a different flask.
D. Attach the connector at the free end of the plastic tubing to the Pressure Sensor with a clockwise turn. Close the two-way valve at the stopper by turning it perpendicular to the valve stem to ensure that the air sample to be studied is confined to the flask.
E. Set out in the room are a number of water baths for you to use to attain different temperatures. Obtain the boiling water bath using hot mitts and bring it back to your station. You want to use the boiling water bath first, because if your stopper pops out, you will have to start again….and the stopper is most likely to pop out in the highest
temperature water bath.
F. Click the green “Collect” button in the LoggerPro program. Place the flask with your air sample into the boiling water bath. Make sure the entire flask is covered (as in Figure 3). Place the temperature probe into the water bath.
Figure 2
Figure 3
G. When the pressure reading in the lower left-hand corner of the program has stabilized, click “Keep” to save your first data point. H. Return the water bath you were using and obtain the next water bath (any temperature bath can be used at this point. Using the same procedure as you did for the boiling water bath, collect a pressure and temperature data point for this water bath. Return the water bath to its appropriate location. I. Repeat Step H until you have accumulated four different temperature points. You should see some change in pressure as you changed temperature. If not pressure change took place as you changed temperature, then you will need to repeat the entire experiment because you had a leak in your system. J. Record the pressure and temperature values in Data Sheet 2.
DATA SHEET 2
Pressure(kPa)
Temperature(°C)
Temperature(K)
Constant, k(P / T or P•T)
K. Since for all gases temperature must be in K, you will need to change the temperature on the x-axis to K. To do so, from the “Data” menu, select “New Calculated Column.” Enter “Temp Kelvin” as the name, “T Kelvin” as the short name, and “K” as the unit. In the ”Expression” box, enter “273+” and then from the “Variable(Column)” button select “Temperature.” In the “Expression” box, you should now see 273+”Temperature”
displayed. Click “Done” and a new column should be created. L. On the graph, click on the independent variable axis name and select “Temp Kelvin” to be displayed on the x-axis.
M. In the “Analyze” menu, select “Autoscale” to rescale your data to fit the window. 1. If your data appears to display a linear relationship (meaning you have a direct relationship), go to the “Analyze” menu and select “Linear Fit” to get the best-fit
linear regression. 2. If your data does not appear to display a linear relationship (meaning you have an inverse relationship), you will need to graph the data in a different way. a. From the “Data” menu select “New Calculated Column.” Enter “1/Temperature”
as the Name, “1/T” as the shortname, and “1/K” as the unit. b. In the “Expression” box type “1/” then select “Temp Kelvin” from the “Variables (Columns)” list. In the “Expression” box, you should see displayed 1/”Temp Kelvin”. Click “Done” when you are ready. c. On the graph, click on the independent variable axis name and select
“1/Temperature” to be displayed on the x-axis.
d. In the “Analyze” menu, select “Autoscale” to rescale your data to fit the window. e. If the relationship now appears to be linear, go to the “Analyze” menu and select
“Linear Fit” to create a best-fit linear regression.
V. Once you have a linear regression fit completed, print out copies of the graph for you and your lab partner by going to the “File” menu and selecting “Print Graph.” Be sure to include a copy of the graph when you turn in your lab. W. Using the information from your graph, write an algebraic equation that expresses the relationship between the two measured variables. Remember to follow the format for this equation as illustrated on page 11. Be sure to use the names of the variables and correct units for the variables, slope, and intercept.
X. Discuss the quality (precision) of your data by providing specific references to your graph. Y. In this experiment, what two experimental factors were assumed to be kept constant? Z. Using your algebraic equation, determine the pressure for the following temperatures. Show your calculations. 200. K: 400. K: AA.What happens to the pressure when the temperature of the gas doubles from 200 K to 400 K? BB.Since Guy-Lussac’s law states that the relationship between pressure and temperature is a constant, determine the value of the constant, k. To do this, go back to how you made your graph—did you determine the original relationship was direct or inverse? If the relationship was direct, then calculate k = P/T. If the relationship was inverse, then calculate k = PT. Record the values for each of your data points in Data Sheet 2.
How constant were the values for k that you obtained? Good data may show some minor variation, but the values for k should be relatively constant.
QUESTIONS :
1a) Charles' Law states that the relationship between volume and temperature of an ideal gas is direct. What would you expect a graph of volume (dependent) vs. temperature (independent) to look like?
1b) How would you go about calculating the constant for a graph of the type in question 1?
1c) Explain what two variables should be held constant for a Charles' Law type of experiment.
1d) In the first part of the actual lab, you will be looking at the pressure relationship with volume. Explain why you would need to start the experiment over if the syringe becomes disconnected from the gas pressure sensor. In other words, in the experiment you are actually doing in lab, what variables need to be held constant?
1e )In the second part of the actual lab, you will be looking at the pressure relationship with temperature. Explain why you would need to start the experiment over if the stopper in the flask is left open to the atmosphere during the entire experiment. In other words, in the experiment you are actually doing in lab, what variables need to be held constant?
Explanation / Answer
1 a) Charles' Law states that volume is directly proportional to temperature given a constant amount of gas and a constant pressure. The key is that temperature is the independent variable in Charles' Law. If you change volume, you change pressure, and then Charles' Law no longer holds. This law is also one-way; pressure is dependent on volume in this relationship. In the real world, you can't directly change pressure; a pressure change is the result of a change to some other variable in the gas laws
1 b)
Gay-Lussac's work of combining volumes, found that pressure and temperature are directly related; increase pressure and you increase temperature, and vice-versa. This relationship, however, is relatively interdependent, because other determinants of pressure can be varied independently of temperature without violating any declared constants in Amontons' Law.gas law, PV = nRT , retains the mathematical relationships between amount of gas, volume, temperature and pressure, however it more or less loses some of the subtleties of cause and effect.
changing volume will directly change pressure in the opposite direction, limiting the net change on the left side of the equation. Only if there is a net change in the product of pressure and volume for a constant amount of gas will the temperature change to balance the equation.
1 c) Pressure and the number of moles of gas only for a Charles' Law type of experiment.
1 d) in the experiment i am actually doing in lab Pressure and Temperature should be held constant.
1 e) The volume of the gas is equal to the volume of the flask. To find this, first calculate the mass of water that filled the flask. Then, assuming that the water’s density is 0.99802 g/mL, calculate the volume. The number of moles of gas is calculated using the Ideal Gas Law.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.