Gas Laws Name Date Block Introduction One of the most amazing things about gases is that, despite wide differences in chemical properties, all the gases more or less obey the gas laws. The gas laws deal with how gases behave with respect to pressure, volume, temperature, and amount. Pressure Gases are the only state of matter that can be compressed very tightly or expanded to fill a very large space. Pressure is force per unit area, calculated by dividing the force by the area on which the force acts. The earth's gravity acts on air molecules to create a force, that of the air pushing on the earth. This is called atmospheric pressure. The units of pressure that are used are pascal (Pa), standard atmosphere (atm), and torr. 1 atm is the average pressure at sea level. It is normally used as a standard unit of pressure. The SI unit though, is the pascal. 101,325 pascals equals 1 atm. For laboratory work the atmosphere is very large. A more convient unit is the torr. 760 torr equals 1 atm. A torr is the same unit as the mmhg (millimeter of mercury). It is the pressure that is needed to raise a tube of mercury 1 millimeter. The Gas Laws: Pressure Volume Temperature Relationships Directions: Describe what contribution each of the Scientist below made to the Gas Laws and include there gas law equation. Boyle's Law Robert Boyle (1627-1691)
Charles' Law Jacques Charles (1746-1823) Gay-Lussac's Law Joseph Gay-Lussac (1778-1850)
Avogadro's Law Amedeo Avogadro (1776-1856) Partial Pressures John Dalton (1766-1844)
Non-Ideal Gases Johannes Diderik van der Waals (1837-1923) What is the idealthe Ideal Gas Law
Gas Laws Chapter 13: Book Problems Page 435-437 Questions and Problems 13.1 Pressure Questions 1. How are the three states of matter similar, and how do they differ? 2. What is meant by the pressure of the atmosphere? What causes this pressure? 3. Describe a simple mercury barometer. How is such a barometer used to measure the pressure of the atmosphere? Problems 4. Convert the following pressures into atmospheres. a. 105.2 kpa b. 75.2 cm Hg 5. Convert the following pressures into units of mm Hg. a. 0.9975 atm b. 225,400 Pa
13.2 Pressure and Volume: Boyle s Law Problems 6. For each of the following sets of pressure/volume data, calculate the missing quantity. Assume that the temperature and the amount of gas remain constant. a. V = 53.2 ml at 785 mm Hg; V =? at 700 mm Hg b. V = 2.25 L at 1.67 atm; V = 2.00 L at? atm 7. For each of the following sets of pressure/volume data, calculate the missing quantity. Assume that the temperature and the amount of gas remain the same. a. V = 291 ml at 1.07 atm; V =? at 2.14 atm b. V = 1.25 L at 755 mm Hg; V =? at 3.51 atm 13.3 Volume and Temperature: Charles s Law Questions 8. What is meant by the absolute zero of temperature? 9. How can Charles s law be used to determine absolute zero? Problems 10. If a 45.0-mL sample of gas at 26.5 C is heated to 55.2 C, what is the new volume of the gas sample (at constant pressure)?
11. For each of the following sets of volume/temperature data, calculate the missing quantity. Assume that the pressure and the mass of gas remain constant. a. V = 25.0 L at 0 C; V = 50.0 L at? C b. V = 247 ml at 25 C; V = 255 ml at? C 12. The label on an aerosol spray can contains a warning that the can should not be heated to over 130 F because of the danger of explosion due to the pressure increase as it is heated. Calculate the potential volume of the gas contained in a 500.-mL aerosol can when it is heated from 25 C to 54 C (approximately 130 F), assuming a constant pressure. 13.4 Volume and Moles: Avogadro s Law Problems 13. If 0.214 mol of argon gas occupies a volume of 652 ml at a particular temperature and pressure, what volume would 0.375 mol of argon occupy under the same conditions? 19. If 46.2 g of oxygen gas occupies a volume of 100. L at a particular temperature and pressure, what volume will 5.00 g of oxygen gas occupy under the same conditions?
20. As weather balloons rise from the earth s surface, the pressure of the atmosphere becomes less, tending to cause the volume of the balloons to expand. However, the temperature is much lower in the upper atmosphere than at sea level. Would this temperature effect tend to make such a balloon expand or contract? Weather balloons do, in fact, expand as they rise. What does this tell you? 13.5 The Ideal Gas Law Questions 21. Under what conditions do real gases behave most ideally? 22. Show how Boyle s law can be derived from the ideal gas law. Problems 23. Given each of the following sets of values for an ideal gas, calculate the unknown quantity. a. P = 782 mm Hg; V =?; n = 0.210 mol; T = 27 C b. P =? mm Hg; V = 644 ml; n = 0.0921 mol; T =303 K 24. Given each of the following sets of values for an ideal gas, calculate the unknown quantity. a. P = 1.01 atm; V =?; n = 0.00831 mol; T = 25 C b. P =? atm; V = 602 ml; n = 8.01 x 10-3 mol; T = 310 K
Gas Law Thinking Skills 25. What distinguishes effusion from diffusion? How are these processes similar? 26. Explain what each of the following changes would do to the pressure in a closed container (increase or decrease pressure). A) Part of the gas is removed, B) The container size (volume) is decreased, and C) Temperature is increased. 27. Complete the Conversion Factors for the following: (cf. page A10 textbook) 1 atmosphere = mm Hg 2 atmosphere = mm Hg torr torr kilopascals kilopascals pascal pascal 28. Graph the following as the heat increases:
29. Circle the letter next to each sentence that is true concerning the compressibility of gases. a. The large relative distances between gas particles means that there is considerable empty space between them. b. The assumption that gas particles are far apart explains gas compressibility. c. Compressibility is a measure of how much the volume of matter decreases under pressure. 30. If you notice that a sealed bag of potato chips bulges when placed near a sunny window, what can you hypothesize about the relationship between the temperature and pressure of an enclosed gas?. 31. List three basic assumptions of the kinetic theory about the properties of gases. 1, 2. 3. Questions 32, 33, 34, and 35 refer to the graph. This graph represents the relationship between pressure and volume for a sample of gas in a container at a constant temperature. 32. P 1 V 1 33. P 2 V 2 34. P 3 V 3 35. What do you notice about the product of pressure times volume at constant temperature? What gas law does this illustrate?.
Physical Characteristics of Gases Activity: Gas Law Animations Purpose: for students to discover the relationship between variables in gas samples: amount (mass), volume, pressure, speed, and temperature Using the websites below, find the links to the correct animations on the Lessons page. Using the directions below for use of each animation, determine the relationship between the requested variables. Record your observations and data on the page provided. A: http://jersey.uoregon.edu/vlab/piston/ B: http://www.chem.iastate.edu/group/greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.html C: http://www.grc.nasa.gov/www/k-12/airplane/animation/frglab2.html D: http://www.chemistry.ohio-state.edu/betha/nealgaslaw/fr2.2.html Temperature and Pressure (constant volume and amount)- Site A a. Choose the constant volume button b. Drag the black tip on the red line inside the thermometer to various temperatures c. As you do this, a graph containing your points should appear d. Once you have created at least ten points, record your information 2. Pressure and Volume (constant temperature and amount)- Site B a. Drag the plunger to change the volume of the gas (in ml) b. the chart will display the pressure for that volume of gas c. When you have at least ten points with varying volumes, press Graph d. record your information
3. Amount (mass) and Volume (constant pressure and temperature)- Site C a. In the box on the left, freeze one of the constant variables; then choose the second to freeze b. Choose Effect of Changing Mass on Volume c. Observe the movement d. Record your information e. Choose New Case from left 4. Amount (mass) and Temperature (constant volume and pressure)- Site C a. In the box on the left, freeze one of the constant variables; then choose the second to freeze b. Choose Effect of Changing Mass on Temperature c. Observe the movement d. Record your information e. Choose New Case from left 5. Volume and Temperature (constant pressure and amount)- Site C a. In the box on the left, freeze one of the constant variables; then choose the second to freeze b. Choose Effect of Changing Temperature on Volume c. Observe the movement d. Record your information 6. Amount (mass) and Pressure (constant volume and temperature)- Site D a. Press the Add Gas or Remove Gas button until you see a distinct change in the number of particles b. Observe the change in the yellow pressure gauge at the top of the animation. c. Record your information. To sketch the graph, you will need to compare the relationship to another set of variables that you already have the graph drawn for. 7. Speed (velocity) and Temperature- Site D a. Draw the red line in the thermometer to a higher temperature b. Observe the change in movement of the particles c. Record your information. To sketch the graph, you will need to compare the relationship to another set of variables that you already have the graph drawn for. 8. Conformation- Site D a. Using Site D, confirm the results from Test 1: As you move the temperature up and down, observe the effects of temperature change on pressure (the yellow gauge at the top). b. Using Site D, confirm the results of Test 2: As you move the plunger (adjusting the volume) up or down, observe the effects of volume change on pressure (yellow gauge at the top).
Fill in the chart below with your observations and collected data. Under Change, record what you changed and how it affected the other variable. For example: Increased volume, decreased pressure. Under Proportionality, record whether the two variables are directly or inversely proportional. Under Graph, sketch the shape of the graph created by these two variables (you do not need to add numbers). Variables Change Proportionality Graph 1 Temperature and Pressure 2 Pressure and Volume 3 Amount and Volume 4 Amount and Temperature 5 Volume and Temperature 6 Amount and Pressure 7 Speed and Temperature