2 From last chapter… Kinetic Molecular Theory Particles in an ideal gas…have no volume.have elastic collisions.are in constant, random, straight-line motion.don’t attract or repel each other.have an avg. KE directly related to Kelvin temperature.
3 Real Gases Particles in a REAL gas… Gas behavior is most ideal… have their own volumeattract each otherGas behavior is most ideal…at low pressuresat high temperaturesin nonpolar atoms/molecules
4 Properties of GasesCompressibility – gases are easily compressed because of the space between the particles in a gasGases expand to take the shape and volume of their container
5 Factors Affecting Gas Pressure Amount of gas – more particles have more collisions with the container walls and thus create more pressureVolume – if you reduce the volume of the container, the particles are more compressed and exert a greater pressure on the walls of the containerTemperature – increasing temperature increases the kinetic energy of the particles, which then strike the walls of the container with more energy
6 Remember? Units of Pressure KEY UNITS AT SEA LEVELkPa (kilopascal)1 atm760 mm Hg760 torr14.7 psi*These are all equivalent amounts of pressure
7 Standard Temperature & Pressure STPStandard Temperature & Pressure0°C K1 atm kPa-OR-
9 Boyle’s LawThe pressure and volume of a gas are inversely relatedat constant mass & tempP1V1 = P2V2PV
10 Gas Law Problem BOYLE’S LAW P V A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa.BOYLE’S LAWGIVEN:V1 = 100. mLP1 = 150. kPaV2 = ?P2 = 200. kPaPVWORK:
11 Charles’ LawThe volume and absolute temperature (K) of a gas are directly relatedat constant mass & pressureVT
12 Gas Law Problem CHARLES’ LAW T V A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.CHARLES’ LAWGIVEN:V1 = 473 cm3T1 = 36°C = 309KV2 = ?T2 = 94°C = 367KTVWORK:
13 Gay-Lussac’s LawThe pressure and absolute temperature (K) of a gas are directly relatedat constant mass & volumePT
14 Gas Law Problem GAY-LUSSAC’S LAW P T A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be torr?GAY-LUSSAC’S LAWGIVEN:P1 = 765 torrT1 = 23°C = 296KP2 = 560. torrT2 = ?PTWORK:
16 Gas Law Problem COMBINED GAS LAW P T V V1 = 7.84 cm3 P1 = 71.8 kPa A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.COMBINED GAS LAWGIVEN:V1 = 7.84 cm3P1 = 71.8 kPaT1 = 25°C = 298 KV2 = ?P2 = kPaT2 = 273 KP TVWORK:
17 Avogadro’s LawThe volume and number of moles of a gas are directly relatedat constant temperature & pressureVn
18 Gas Law Problem AVOGADRO’S LAW n V GIVEN: V1 = 36.7 L n1 = 1.5 mol Consider two sample of N2 gas. Sample 1 contains 1.5 mol of N2 and has a volume of 36.7 L at 25°C and 1 atm. Sample 2 has a volume of 16.5 L at 25°C and 1 atm. Calculate the number of moles of N2 in Sample 2.AVOGADRO’S LAWGIVEN:V1 = 36.7 Ln1 = 1.5 molV2 = 16.5 Ln2 = ?nVWORK:
19 UNIVERSAL GAS CONSTANT Ideal Gas LawPV=nRTUNIVERSAL GAS CONSTANTR= Latm/molKR=8.315 dm3kPa/molK
20 Ideal Gas Law Problem P = ? atm n = 0.412 mol T = 16°C = 289 K Calculate the pressure in atmospheres of mol of He at 16°C & occupying 3.25 L.GIVEN:P = ? atmn = molT = 16°C = 289 KV = 3.25 LR = Latm/molKWORK:
21 14.4 - Dalton’s Law of Partial Pressures The partial pressure of a gas is the pressure that the gas would exert if it were alone in the container.Dalton’s Law of Partial Pressures says that the total pressure of a mixture of gas is equal to the sum of the partial pressures of all gases in the mixture. Or,Ptotal = P1 + P2 + P3 +…Note: you can calculate the partial pressures of the gases if they behave ideally using the ideal gas law (P = nRT/V)
22 Dalton’s Law ExampleA 2.0 L flask contains a mixture of nitrogen gas and oxygen gas at 25°C. The total pressure of the gaseous mixture is 0.91 atm, and the mixture is known to contain mol of N2. Calculate the partial pressure of oxygen and the moles of oxygen present.
23 Graham’s Law of Effusion Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughoutEffusion is when a gas escapes through a tiny hole in its containerGases of lower molar mass diffuse and effuse faster than gases of higher molar mass
24 Graham’s Law of Effusion The rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass.This equation compares effusion rates for two gases
25 Graham’s Law ProblemCalculate the ratio of the velocity of hydrogen molecules (H2) to the velocity of carbon dioxide (CO2) molecules at the same temperature.
26 Gas Stoichiometry Yes, we are going back to those 3 step problems… Molar volume of a gas is the volume that is occupied by 1 mol of an ideal gas at STP.1 mol of gas occupies 22.4 LYes, we are going back to those 3 step problems…
27 Gas Stoichiometry Problem Quicklime, CaO, is produced by heating calcium carbonate. Calculate the volume of carbon dioxide produced at STP from the decomposition of 152 g of calcium carbonate according to the reaction CaCO3 (s) CaO (s) + CO2 (g)