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Gas Laws

Gas Laws. The gas laws are simple mathematical relationships between pressure, volume, temperature, and the amount of a gas. They were developed by scientists who experimented with a variety of gases and were able to observe the relationships among these variables. Boyle’s Law.

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Gas Laws

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  1. Gas Laws

  2. The gas laws are simple mathematical relationships between pressure, volume, temperature, and the amount of a gas. • They were developed by scientists who experimented with a variety of gases and were able to observe the relationships among these variables.

  3. Boyle’s Law • What happens to the volume of a gas when you increase the pressure? • What happens to the pressure when you increase the volume? • Boyle’s Law relates the volume and pressure of a gas. It assumes that the temperature and the number of gas particles remain constant/

  4. represent initial conditions while represent a different set of conditions. • If you have any three of the values, you can calculate the fourth. • The units of pressure and volume MUST be the same on both sides of the equation!

  5. A balloon filled with helium gas has a volume of 500. mL at a pressure of 1.00 atm. The balloon is released into the air. When the balloon is high enough that the pressure is 0.750 atm, what is the volume of the gas?

  6. The volume of a sample of gas is 425 mL at a pressure of 1.05 atm. What would be the pressure of the gas, in kPa, if the volume is decreased to 215 mL while the temperature is held constant?

  7. Charles’ Law • If the temperature of a gas increases, but the pressure stays the same, what will happen to the volume of the gas? • Charles’ Law is the mathematical relationship between temperature and volume. • It assumes that the pressure and the number of gas particles remain constant.

  8. What would happen if one of the temperatures was a negative number?

  9. To solve the problem of negative temperatures, the Kelvin temperature scale is used for all gas laws. • The lowest temperature in the Kelvin scale is 0K, also known as absolute zero. Note that no degree symbol is used with the Kelvin scale. • To convert from oC to K, simply add 273. • This means that the magnitude of a celsius degree and a Kelvin is exactly the same, the Kelvin scale has just been moved downward by 273 degrees. • Therefore, absolute zero is 0K or -273oC

  10. A sample of neon gas has a volume of 752 mL at 25.0oC. What will the volume be at 100.oC if the pressure is constant?

  11. A sample of nitrogen gas has a volume of 375 mL at a temperature of 0.0oC. If the gas is heated and the volume increases to 500. mL, what is the new temperature of the gas (in Celsius degrees)?

  12. Gay-Lussac’s Law • Gay-Lussac’s Law relates the pressure and temperature of a gas while the volume is held constant. • If the temperature of a gas decreases, what will happen to the pressure?

  13. Don’t forget that the temperature MUST be in Kelvins.

  14. At 125oC, the pressure of a sample of oxygen is 764 mm Hg. What will be the pressure of the sample if the temperature is increased to 175oC?

  15. A sample of helium gas has a pressure of 115 kPa when the temperature is 22oC. What will be the temperature, in Celsius, if the pressure is reduced to 103 kPa?

  16. Combined Gas Law • In the first 3 gas laws, one variable has been held constant. • Often when a gas sample undergoes changes, pressure, temperature, and volume ALL change. • Boyle’s, Charles’ and Gay-Lussac’s laws can be combined into a single law called the combined gas law.

  17. Note that the combined gas law reduces to each of the 3 other laws, if one variable is held constant.

  18. The volume of a gas is 32.5 mL at 22oC and 0.985 atm. What will be the volume of the gas at STP?

  19. A sample of fluorine gas occupies 1.5 L at 26.5oC and 1.00 atm. What will be the pressure of the gas if the volume increases to 2.5 L and the temperature increases to 40.0oC?

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