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Gas Laws
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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
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Gas Pressure Gas molecules move from an area of higher pressure to area of lower pressure Opening a can/bottle of soda
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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.
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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
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Boyle’s Law Continued P1V1 = P2V2
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Practice Air in a container occupies mL at 1.08 atm. What volume must the container be to have a pressure of 1.43 atm? mL
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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
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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: mL The pressure of a sample of He in a 1.00 L container is atm. What is the new pressure if the sample is placed in a 2.00 L container? Answer: atm
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Kelvin Scale and Charles’ Law
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Temperature Scales SI scale: degree Celsius (°C) or Kelvin (K)
English scale: degree Fahrenheit (°F) °C = 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
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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
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Charles’ Law
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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: °C
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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: L What is the volume of the air in a balloon that occupies L at 25 °C if the temperature is lowered to 0.00 °C. (convert temps. to Kelvin) Answer: L
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Lussac’s Law Joseph Gay-Lussac explored the relationship between temperature and pressure. Direct relationship
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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
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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
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Pratice A He filled balloon at sea level has a volume of 2.1L at atm and 36°C. If it released and rises to an elevation at which the pressure is atm and the temperature is 28°C, what will be the new volume of the balloon? Answer: 1.81L
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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
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PV=nRT Ideal Gas Law P- pressure (atm or kPa) V- volume (L)
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)
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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 If pressure in kPa use 8.314
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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.
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Practice If the pressure exerted by a gas at 25°C in a volume of L is 3.81atm, how many moles of gas are present? Answer: 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
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Practice Calculate the volume that a mol sample of a gas will occupy at 265 K and a pressure of atm. Answer: 7.8 L What is the pressure in atmospheres of a mol sample of He gas at a temperature of 20°C if its volume is 0.505L? Answer: atm
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Equations and Information
PV=nRT R= R= 8.314 R= 62.4 P1V1 = P2V2 1 atm = kPa 1 atm = 760 mmHg Convert All Temperatures To Kelvin
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