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Published byMara Regan Modified about 1 year ago

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Gases are fluids ◦ Fluids are any substance that flows Gases are highly compressible ◦ Example: Tire pressure Gases completely fill containers Gases have lower densities than liquids and solids

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KMT describes the motion of the particles ◦ Particles have the same motion as billiard balls /GasLaw/GLP.htm

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Assumptions: ◦ Gas molecules are in constant, random motion ◦ Gas molecules are separated by large distances ◦ Gas molecules have no attractive/repulsive forces ◦ Collisions are considered to be perfectly elastic ( no energy is lost )

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Temperature and energy of gases are directly proportional ◦ As the temperature increases, kinetic energy of the molecules increases ◦ As temperature decreases, kinetic energy will also decrease

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At sea level, the standard gas pressure is 1 atmosphere Pressure is the force exerted by gas molecules Standard Temperature and Pressure (STP) is equal to 1 atm and 0 °C. Note:1 ATM is measured from the surface of the ocean (sea level) to the top of the sky (stratosphere)

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Atmosphere ( atm) Torr / millimeter of mercury mm Hg Pounds per square inch (psi) Pascal of kilo Pascal (Pa or kPa) Conversions vs. 1 ATM 760 mm Hg or Torr 14.7 psi kPa

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Convert 72.7 atmospheres (atm) into kilopascals (kPa) Convert 31.2 psi to ATM

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Variables in Gas Equations: ◦ P = Pressure (kPa or atm) ◦ V = Volume (L) ◦ T = Temperature (K) ◦ n = amount of gas (moles)

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States that for a fixed amount of gas at constant temperature the volume of the gas is inversely proportional to the pressure of a gas Pressure Volume

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Example Problem ◦ The pressure on 2.50 L of anesthetic gas changes from 105 kPa to 40.5 kPa. What will be the new volume if the temperature remains constant?

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Example Problem ◦ A high-altitude balloon contains 30.0 L of helium gas at 103 kPa. As the balloon rises, you record a new volume of 35.0 L. What is the atmospheric pressure in kPa? (Assume constant temperature)

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States that the volume of a gas is directly proportional to the Kelvin temperature if the pressure remains constant Volume Temperature

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Example Problem ◦ The air in a hot air balloon has a volume of L at 30.0°C (303 K). What will the volume be if the temperature is raised to °C (393 K)?

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Example Problem ◦ An aerosol can has a volume of 3.00 x 10 2 mL at 150.0°C is heated until its volume is 6.00 x 10 2 mL. What is the new temperature (in K) of the gas if pressure remains constant?

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States that the pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant Pressure Temperature

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Example Problem ◦ The gas left in a used aerosol can is at a pressure of 103 kPa at 25 ° C. If this can is thrown onto a fire, what is the pressure of the gas when its temperature reaches 928 ° C?

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Example Problem ◦ A sealed cylinder of gas contains nitrogen gas at 1.00 x 10 3 kPa pressure and a temperature of 20.0 ° C. The cylinder is left in the sun, and the temperature of the gas increases to 50.0 ° C. What is the new pressure in the cylinder?

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A single equation that combines all the gas laws:

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Example Problem ◦ A gas takes up a volume of 17 liters, has a pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas?

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Relates the gas laws and the amount of gas Requires the gas constant, R ◦ R can be a different number depending on the units

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Example Problem ◦ A container of 3.0 L of nitrogen (N 2 ) is at a pressure of 4.5 x 10 2 kPa and a temperature of 39 ° C. How many grams of N 2 are in the container?

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Example Problem ◦ What pressure will be exerted by mol of a gas at 25.0 °C if it is contained in a L vessel?

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Equal volumes of gases at the same temperature and pressure contain equal numbers of particles Due mainly to the large amount of empty space between particles ◦ From this, scientists have determined that 1 mol = 22.4 L at STP

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Why? ◦ Tennis balls vs. Bowling balls

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