Unit 9: The Gas Laws 9.5 1. Write the formula for the density of any gas at STP. Name: KEY Text Questions from Corwin density (in g/l) = molar mass in grams / molar volume in liters (i.e., 22.4 L) Ch. 11 2. How did Robert Boyle envision air? as being composed of invisible particles that can be squeezed closer together 11.1 3. List five main properties of gases. they have an indefinite shape, can expand, can compress, have low densities, mix completely w/other gases in the same container 11.2 4. The pressure a gas exerts depends on what two things? how hard and how often the particles strike the walls of the container 5. Why does gas pressure increase as the temperature increases? because the m cules move faster and collide more frequently and w/more energy at higher temp 6. Atmospheric pressure is about how many pounds per square inch? 15 psi 7. Who invented the barometer, and what does it do? Torricelli; it measures atmospheric pressure 8. Standard pressure is 1 atm, but it is also _760 torr_, where 1 torr equals 1 mm Hg 11.3 9. List the three ways to change the number of collisions (i.e., the pressure) of gas molecules. increase or decrease volume of container, temp of gas, or # of m cules in container 11.4 10. What does Boyle s law state? the volume of a gas is inversely proportional to the pressure when the temp remains constant 11.5 11. What does Charles law state? the volume of a gas is directly proportional to the Kelvin temp if the pressure remains constant 11.6 12. What does Gay-Lussac s law state? the pressure of a gas is directly proportional to the Kelvin temp if the volume remains constant 11.7 13. Write the equation for the combined gas law. P 1 V 1 /T 1 = P 2 V 2 /T 2
14. Write two values of standard temperature and two values for standard pressure. ST: 0 o C and 273 K SP: 760 mm Hg, 760 torr 11.8 15. What is the vapor pressure? the P exerted by the gaseous vapor above a liquid when rate of evap = rate of condensation 16. Why does the vapor pressure increase as the temperature increases? because liquid m cules evaporate faster and vapor m cules have more kinetic energy 11.9 17. What does Dalton s law of partial pressures state? the total pressure of a gaseous mixture = the sum of the individual pressures of each gas in the mix 18. Write the equation for Dalton s law and define the terms. P total = P 1 + P 2 + P total = mixture pressure; P 1, P 2, etc = partial pressure of each gas 19. What is a partial pressure? the pressure exerted by each gas in a mixture of gases 20. In the volume-by-water-displacement method of collecting gases, what two things are equal? volume of collected gas and volume of water displaced 21. When hydrogen gas is collected over water, which two gases are in the graduated cylinder? hydrogen and water vapor 22. What does it mean if a collected gas is wet? that the gas was collected over water 11.10 23. What did James Joule suggest? that the temp of a gas is related to the energy of its m cules 24. What is the difference between an ideal gas and a real gas? ideal: always behaves predictably; real: does NOT behave ideally under all conditions 25. Under what two conditions do real gases NOT behave ideally? low temperatures and high pressures 26. List the five assumptions that make up the kinetic theory of gases. gases are made up of tiny m cules; m cules move quickly, randomly, and in straight lines; m cules have no attraction for each other; m cules undergo elastic collisions; KE is proportional to T 27. Even for different gases, when is the average kinetic energy equal? at the same temperature
28. If samples of hydrogen and oxygen are at the same temperature, which molecules move faster, and why? H 2 m cules move faster because they are lighter 29. What is absolute zero? the temperature at which the pressure and volume of a gas theoretically reach zero 30. Give the value of absolute zero, in two different units. 273 o C or 0 K 31. What is unique about an ideal gas if it were to reach absolute zero? it would have no KE and no molecular motion 11.11 32. Write the equation for the ideal gas law. PV = nrt 33. What is the constant R called, and what is its value, according to the text? R is the ideal gas constant; 0.0821 atm-l/mol-k 34. What three things must be true, in order to use the value for R that you wrote in answering Q33? P must be in atm, V in L, and T in K
Unit 9: The Gas Laws 9.5 1. Write the formula for the density of any gas at STP. Name: Text Questions from Corwin Ch. 11 2. How did Robert Boyle envision air? 11.1 3. List five main properties of gases. 11.2 4. The pressure a gas exerts depends on what two things? 5. Why does gas pressure increase as the temperature increases? 6. Atmospheric pressure is about how many pounds per square inch? 7. Who invented the barometer, and what does it do? 8. Standard pressure is 1 atm, but it is also, where 1 torr equals 11.3 9. List the three ways to change the number of collisions (i.e., the pressure) of gas molecules. 11.4 10. What does Boyle s law state? 11.5 11. What does Charles law state? 11.6 12. What does Gay-Lussac s law state? 11.7 13. Write the equation for the combined gas law.
14. Write two values of standard temperature and two values for standard pressure. 11.8 15. What is the vapor pressure? 16. Why does the vapor pressure increase as the temperature increases? 11.9 17. What does Dalton s law of partial pressures state? 18. Write the equation for Dalton s law and define the terms. 19. What is a partial pressure? 20. In the volume-by-water-displacement method of collecting gases, what two things are equal? 21. When hydrogen gas is collected over water, which two gases are in the graduated cylinder? 22. What does it mean if a collected gas is wet? 11.10 23. What did James Joule suggest? 24. What is the difference between an ideal gas and a real gas? 25. Under what two conditions do real gases NOT behave ideally? 26. List the five assumptions that make up the kinetic theory of gases. 27. Even for different gases, when is the average kinetic energy equal?
28. If samples of hydrogen and oxygen are at the same temperature, which molecules move faster, and why? 29. What is absolute zero? 30. Give the value of absolute zero, in two different units. 31. What is unique about an ideal gas if it were to reach absolute zero? 11.11 32. Write the equation for the ideal gas law. 33. What is the constant R called, and what is its value, according to the text? 34. What three things must be true, in order to use the value for R that you wrote in answering Q33?