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Gas Laws

Gas Laws. Consider the following questions: ·Why should you never leave an aerosol can in your car or trunk in the heat of the summer? ·Why is the first lesson in scuba diving to NOT hold your breath as you ascend?

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Gas Laws

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  1. Gas Laws

  2. Consider the following questions: ·Why should you never leave an aerosol can in your car or trunk in the heat of the summer? ·Why is the first lesson in scuba diving to NOT hold your breath as you ascend? ·What happens to a bag of potato chips packed at sea level but then brought to the mountains?

  3. Gas Laws explore the relationships between properties of gases and allow us to apply mathematical calculations based on these laws. Properties of gases are related to each other through the gas laws Properties of gases ·Volume ·Pressure ·Temperature ·# of moles ·molar mass ·density

  4. Pressure: force exerted by gas molecules when they collide with each other and against the sides of a container. Gas molecules are in constant motion. They have kinetic energy. Pressure is measured in atm, mm Hg, kPa, torr and psi 1 atm = 760 mm Hg = 760 torr = 101.3 kPal Using dimensional analysis we can convert between any unit of measurement of pressure.

  5. Convert the following measurements of pressure: 144 kPa = ? atm 669 torr = ? kPa 795 mm Hg = ? atm 1.05 atm = ? mm Hg

  6. Temperature: measured in Kelvin. Kelvin scale is calibrated not on boiling and freezing points, but on motion of atoms and molecules Absolute zero: theoretical temperature where all atomic motion stops No negative temperatures in Kelvin scale Kelvin = Celsius + 273

  7. Kinetic Molecular Theory (KMT): explains the behavior of gases in terms of particles in motion ·Gases consist of tiny particles-atoms or molecules ·Gas particles are in constant motion-they move in random straight lines and collide with each other and the walls of the container ·Average kinetic energy is directly proportional to temperature ·Gas particles are not attracted or repelled from one another ·Gas particle collisions are perfectly elastic-no energy is gained or lost ·Volume of gas particle itself is insignificant compared to volume of space between particles

  8. KMT is based on ideal gases. no such gases exist attractive forces do exist between particles Gases are closest to ideal at high temperature and low pressure

  9. Boyle's Law Relates pressure and volume Assumes constant temperature and # of particles Pressure and volume are inversely proportional P1V1 =P2V2 Measurement of pressure and volume must be in same unit (atm, torr, ml, L, etc…)

  10. Solve the following: A balloon is filled with 25 L of air at 1.0 atm pressure. If the pressure is changed to 1.5 atm, what is the new volume?

  11. A balloon is filled with 73 L of air at 1.3 atm. What pressure is needed to change the volume to 43 L?

  12. A gas is collected in a 242 cm3 container. The pressure of the gas in the container is measured at 87.6 kPa. What is the volume of the gas at standard pressure?

  13. Charles' Law Relates volume and temperature Assumes pressure and number of particles is constant Volume and temperature are directly proportional V1 = V2 T1T2 Must convert temperature to Kelvin

  14. Solve the following: What is the temperature of a gas that is expanded from 2.5 L at 25 degrees Celsius to 4.1 L at constant pressure?

  15. What is the final volume of a gas that starts at 8.3 L and 17 degrees Celsius and is heated to 96 degrees Celsius?

  16. A 225 cm3 volume of gas is collected at 57 degrees Celsius. What volume would this gas occupy at standard temperature?

  17. Avogadro's Law States that equal volumes of different gases at the same temperature and pressure will contain the same number of molecules. ·Molar volume is volume one mole occupies at 273 K and 1 atm ·1 mole = 22.4 L Volume of gas is directly proportional to number of moles V1 = V2 n1 n2

  18. Solve the following: Consider two samples of nitrogen gas. Sample 1 has a volume of 36.7 L and contains 1.5 moles. Sample 2 has a volume of 16.5 L at the same temperature and pressure. Calculate the number of moles of Sample 2.

  19. 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?

  20. Gay-Lussac's Law Relates temperature and pressure of a gas Assumes volume and # of particles is constant Temperature and pressure are directly proportional P1 = P2 T1 T2

  21. Solve the following: What is the pressure inside a 0.250 L can of deodorant that starts at 25 degrees Celsius and 1.2 atm if the temperature is raised to 100 degrees Celsius? Volume remains constant.

  22. A 12 oz can of soda starts at STP. If the volume remains constant, at what temperature will the can have a pressure of 2.20 atm?

  23. The Combined Gas Law The gas laws may be combined into a single law which relates two sets of conditions (pressure, volume, temperature) P1V1 P2V2 = T1 T2

  24. A 15 L cylinder of gas at 4.8 atm pressure at 25 degrees Celsius is heated to 75 degrees Celsius and compressed to 17 atm. What is the new volume?

  25. A sample of nitrogen monoxide has a volume of 72.6 ml at a temperature of 16 degrees Celsius and a pressure of 104.1 kPa. What volume will the same sample occupy at 24 degrees Celsius and 99.3 kPa?

  26. Dalton's Law of Partial Pressure Dalton's Law states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture Pt = P1 + P2 +P3 +... The partial pressure is the contribution by any given gas

  27. What is the total pressure in a balloon filled with air if the pressure of the oxygen is 170 mm Hg and the pressure of nitrogen is 620 mm Hg?

  28. In a second balloon the total pressure is 1.30 atm. What is the pressure of oxygen (in mm Hg) if the pressure of nitrogen is 720 mm Hg?

  29. ·Hydrogen was collected over water at 21°C on a day when the atmospheric pressure is 748 torr. The volume of the gas sample collected was 300. mL. The vapor pressure of water at 21°C is 18.65 torr. Determine the partial pressure of the dry gas.

  30. ·A sample of oxygen gas is saturated with water vapor at 27ºC. The total pressure of the mixture is 772 mm Hg and the vapor pressure of water is 26.7 mm Hg at 27ºC. What is the partial pressure of the oxygen gas?

  31. ·When a container is filled with 3 moles of H2, 2 moles of O2 and 4 moles of N2, the pressure in the container is 8.7 atm. The partial pressure of H2 is _____.

  32. The Ideal Gas Law Temperature,volume, pressure and number of moles of a gas are all interrelated One equation can describe this relationship using a constant: theideal gas constant PV = nRT R= ideal gas constant R=0.0821 (L atm)/(mol K) or R=8.314 (L kPa)/(mol K) or R = 62.4 (L mm Hg)/(mol K) Use the ideal gas constant that matches the unit of pressure

  33. How many moles of air are there in a 2.0 L bottle at 19 degrees Celsius and 747 mm Hg?

  34. What is the pressure in atm exerted by 1.8 g of H2 gas in a 4.3 L balloon at 27 degrees Celsius?

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