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The Gas Laws

The Gas Laws. Measuring Pressure. Barometer Manometer. Units: atmosphere, kilopascal, millimeter of mercury, Torr, Pound per square inches. Pressure conversions. 1atm=760mmHg=101.3kpa=14.7psi. Atmospheric pressure (barometer). 1 atm = 101.3 kpa = 760 torr = 14.7 psi =760 mmHg.

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The Gas Laws

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  1. The Gas Laws

  2. Measuring Pressure • Barometer • Manometer • Units: atmosphere, kilopascal, millimeter of mercury, Torr, Pound per square inches.

  3. Pressure conversions • 1atm=760mmHg=101.3kpa=14.7psi

  4. Atmospheric pressure (barometer) • 1 atm = 101.3 kpa = 760 torr = 14.7 psi =760 mmHg

  5. Kinetic Molecular Theory • Gases are fluids • Gases have low density • Gases are highly compressible • Gases completely fill a container and exert pressure equally in all direction • Gases move faster in higher temperature

  6. Atmosphere is a sea of gases • Atmosphere

  7. The main gases of atmosphere • Percentages:

  8. Atmospheric pressure • Pressure= force on a surface divided by the area of that surface. Its unit in SI Pascal. • Pascal = 1 Newton of force meter squared

  9. Standard temperature and pressure • Standard temperature and pressure STP • STP = 0°C and 1 atm • At sea level the atmospheric pressure is equal to 1 atm. • Atmospheric pressure is lower in a higher altitude and higher in the valley

  10. Pressure conversion • Convert 22 atm into Psi • 22atm X 14.7 psi = 323.4 Psi 1 atm Convert 73 kPa into torr 73 kPa X 760 torr = 547.7 torr 101,3 kPa

  11. Green House effect Earth is becoming warmer

  12. Ozone depletion and free radicals Free radicals such as Chlorine atom

  13. Gas Laws • 1) Boyles law: The volume of a gas at constant temperature is inversely proportional to the pressure. P1V1 =P2V2

  14. Problem • A sample of a gas has a volume of 100 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm, if the temperature remains constant? P1V1 =P2V2 • 95.9 mL

  15. Dalton’s Law (partial pressure) • The total pressure is equal to the sum of partial pressure. Ptot= P1+ P2 +…

  16. Problem • At a certain temperature, the vapor pressure of water is 20 mmHg. A gas is collected over water at the same temperature at a total pressure of 720 mm Hg . The partial pressure of the gas in mmHg is.. • 700 mmHg or torr

  17. Charles’s Law • The volume of a gas at constant pressure is directly proportional to the absolute temperature.

  18. Charles’s Law • Hot air balloon

  19. Problem • A gas has a volume of 18 centimeter cube at 25 degree Celsius. If the temperature is increased to 35 C at constant pressure, the new volume will be.. • (Hint) T→ Kelvin = 18.6 cm3

  20. Avogadro’s Law • Gases with equal volumes under the same conditions have an equal number of molecules. • I mole of any gas at STP occupies 22.4 liter of volume. • 22.4 liter of any gas at STP has the same number of molecules or atoms

  21. Problem • Calculate the density of oxygen gas at STP. • Density = mass = Molar Mass volume Molar Volume D = 32 = 1.43 g/cm3 22.4

  22. A sample of oxygen gas has a volume of 7.84 cm3 at a pressure of 71.8 kPa and a temperature of 25 degrees Celsius. What will be the volume of the pressure changes to 101 kPa and the temperature goes down to 0 degrees Celsius? • The formula for combined law is • P1V1 = P2V2 T1 T2

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