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Gas Laws

Gas Laws. Gas Pressure. Gas pressure is the result of gas particles colliding with the walls of the container If the volume and temperature of the container is constant: If gas is added, pressure increases If gas is removed, pressure decreases. Gas Pressure.

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Gas Laws

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  1. Gas Laws

  2. Gas Pressure • Gas pressure is the result of gas particles colliding with the walls of the container • If the volume and temperature of the container is constant: • If gas is added, pressure increases • If gas is removed, pressure decreases

  3. Gas Pressure • Gas molecules move from an area of higher pressure to area of lower pressure • Opening a can/bottle of soda

  4. Gas Laws • Predict the behavior of gases based on four properties: • Amount of gas (moles) • Pressure • Temperature • Volume If one of these properties change, the others change as well.

  5. Boyle’s Law • Irish Chemist • Noticed there is an inverse relationship between the pressure and volume of a gas • if the temperature and moles of the gas are constant • If pressure increases, volume decreases • If volume increases, pressure decreases P1V1 = P2V2

  6. Boyle’s Law Continued P1V1 = P2V2

  7. Practice • Air in a container occupies 145.7 mL at 1.08 atm. What volume must the container be to have a pressure of 1.43 atm? 110.04 mL

  8. Practice • A balloon filled with He has a volume of 4.0L has a pressure of 210 kPa. If the balloon is compressed to 2.5 L, what will the pressure of He inside the balloon? Answer: 336 kPa

  9. Practice • The volume of a gas at 99.0 kPa is 300 mL. If the pressure is increased to 188 kPa, what is the new volume? Answer: 157.9 mL • The pressure of a sample of He in a 1.00 L container is 0.988 atm. What is the new pressure if the sample is placed in a 2.00 L container? Answer: 0.494 atm

  10. Kelvin Scale and Charles’ Law

  11. Temperature Scales • SI scale: degree Celsius (°C) or Kelvin (K) • English scale: degree Fahrenheit (°F) • °C + 273 = Temperature in Kelvin • Kelvin – 273 = temperature in °C • Kelvin scale is based off the Celsius scale. • At 0 K all matter is believed to stop moving • Absolute Zero

  12. Charles’ Law • Jacque Charles- French Physicist • Noticed that the volume of the a gas increased when it is heated, under constant pressure • Direct relationship between temperature and volume

  13. Charles’ Law

  14. Practice • A gas sample at 40.0°C occupies 2.32 L. If the temperature is raised to 75°C, what is the volume of the gas if pressure is constant? Answer: 4.35 L • A gas at 89°C occupies 0.67 L. If the volume is increased to 1.12 L, what the temperature be in degree Celsius? Answer: 148.77 °C

  15. Practice • The Celsius temperature of a 300 L sample of gas is lowered from 80.0 °C to 30.0 °C. What will be the resulting volume of this gas? Answer: 112.5 L • What is the volume of the air in a balloon that occupies 0.620 L at 25 °C if the temperature is lowered to 0.00 °C. (convert temps. to Kelvin) Answer: 0.568 L

  16. Lussac’s Law • Joseph Gay-Lussac explored the relationship between temperature and pressure. • Direct relationship

  17. Practice • A gas in a sealed container has a pressure of 123 kPa at 30.0°C. If the pressure is increased to 201 kPa, what is the new temperature? Answer: 49.02°C • The pressure in an automobile tire is 1.88 atm at 25°C. What will be the pressure if the temperature warms to 37°C? Answer: 2.78 atm

  18. Combined Gas Law • Combines Boyle’s, Charles’s, and Lussac’s Laws. • Shows the relationship between temperature, pressure, and volume if the amount of gas is held constant. P1V1 = P2V2

  19. Pratice • A He filled balloon at sea level has a volume of 2.1L at 0.998 atm and 36°C. If it released and rises to an elevation at which the pressure is 0.900 atm and the temperature is 28°C, what will be the new volume of the balloon? Answer: 1.81L

  20. Practice • At 0.00°C and 1.00 atm pressure, a sample of gas occupies 30.0 mL. If the temperature increased to 30.0°C and the entire gas sample is transferred to a 20.0 mL container, what will the gas pressure inside the container? Answer: 1.66 atm

  21. The properties of a gas under ideal conditions PV=nRT P- pressure (atm or kPa) V- volume (L) n- moles of gas (moles) R- ideal gas constant T- temperature (K) Ideal Gas Law

  22. What is the Ideal Gas Constant? • Determined by a series of experiments • Relates pressure, volume, temperature, and moles. • 2 Ideal Gas Constants • 0.0821 • 8.314 • Which one do you use? • Based on pressure units • If pressure in atm use 0.0821 • If pressure in kPa use 8.314

  23. Practice • Calculate the number of moles of a gas in a 3.0 L vessel at 300.K with a pressure of 1.50 atm.

  24. Practice • If the pressure exerted by a gas at 25°C in a volume of 0.044 L is 3.81atm, how many moles of gas are present? Answer: 0.00685 mol • Determine the Celsius temperature of 2.49 moles of gas contained in a 1 L vessel at a pressure of 143 kPa. Answer: 6.9 K= -266°C

  25. Practice • Calculate the volume that a 0.323 mol sample of a gas will occupy at 265 K and a pressure of 0.900 atm. Answer: 7.8 L • What is the pressure in atmospheres of a 0.108 mol sample of He gas at a temperature of 20°C if its volume is 0.505L? Answer: 5.144 atm

  26. Equations and Information PV=nRT R= 0.0821 R= 8.314 R= 62.4 P1V1 = P2V2 1 atm = 101.3 kPa 1 atm = 760 mmHg Convert All Temperatures To Kelvin

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