Kinetic Molecular Theory of Gases and the Gas Laws

Kinetic Molecular Theory of Gases and the Gas LawsMr. NelsonChemistry

Properties of GasesGases are fluidsFluids are any substance that flowsGases are highly compressibleExample: Tire pressureGases completely fill containersGases have lower densities than liquids and solids

Kinetic Molecular TheoryKMT describes the motion of the particlesParticles have the same motion as billiard balls

http://intro.chem.okstate.edu/NSFCCLI/GasLaw/GLP.htmKinetic Molecular Theory of GasesAssumptions:Gas molecules are in constant, random motionGas molecules are separated by large distancesGas molecules have no attractive/repulsive forcesTemperature of GasesTemperature and energy of gases are directly proportionalAs the temperature increases, kinetic energy of the molecules increasesAs temperature decreases, kinetic energy will also decrease

Pressure of GasesAt sea level, the standard gas pressure is 1 atmospherePressure is the force exerted by gas moleculesStandard Temperature and Pressure (STP) is equal to 1 atm and 0 C

Different Units of PressureUnitAbbreviationAtmosphereatmMillimeter of mercurymm HgPascalPa (Usually, kPa)To convert,1 atm = 760 mm Hg1 atm = 101.3 kPa

Converting Pressure ExampleConvert 72.7 atmospheres (atm) into kilopascals (kPa)The Gas LawsVariables in Gas Equations:P = Pressure (kPa or atm)V = Volume (L)T = Temperature (K)n = amount of gas (moles)

Boyles LawStates that for a fixed amount of gas at constant temperature the volume of the gas is inversely proportional to the pressure of a gas

Boyles LawExample ProblemThe 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?Boyles LawExample ProblemA 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)

Charless LawStates that the volume of a gas is directly proportional to the Kelvin temperature if the pressure remains constant

Charless LawExample ProblemThe air in a hot air balloon has a volume of 400.0 L at 30.0C (303 K). What will the volume be if the temperature is raised to 120.0 C (393 K)?

Charless LawExample ProblemAn aerosol can has a volume of 3.00 x 102 mL at 150.0C is heated until its volume is 6.00 x 102 mL. What is the new temperature (in K) of the gas if pressure remains constant?

Gay-Lussacs LawStates that the pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant

Gay-Lussacs LawExample ProblemThe 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?

Gay-Lussacs LawExample ProblemA sealed cylinder of gas contains nitrogen gas at 1.00 x 103 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?Combined Gas LawA single equation that combines all the gas laws:

Combined Gas LawExample ProblemA 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?

Ideal Gas LawRelates the gas laws and the amount of gasRequires the gas constant, RR can be a different number depending on the units

PV = nRTExample ProblemA container of 3.0 L of nitrogen (N2) is at a pressure of 4.5 x 102 kPa and a temperature of 39 C. How many grams of N2 are in the container?

Ideal Gas LawExample ProblemWhat pressure will be exerted by 0.450 mol of a gas at 25.0 C if it is contained in a 0.650 L vessel?

Avogadros HypothesisEqual volumes of gases at the same temperature and pressure contain equal numbers of particlesDue mainly to the large amount of empty space between particlesFrom this, scientists have determined that 1 mol = 22.4 L at STPThis was not well acceptedWhy?Tennis balls vs. Bowling balls

But its true!