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I. Physical Properties 9 (A) describe and calculate the relations between volume, pressure, number of moles, and temperature for an ideal gas as described by Boyle's law, Charles' law, Avogadro's law, Dalton's law of partial pressure, and the ideal gas law; 9 (B) perform stoichiometric calculations, including determination of mass and volume relationships between reactants and products for reactions involving gases; and 9 (C) describe the postulates of kinetic molecular theory. Gases

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A. Kinetic Molecular Theory b Particles in an ideal gas… have no volume. have elastic collisions. are in constant, random, straight- line motion. dont attract or repel each other. have an avg. KE directly related to Kelvin temperature.

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B. Real Gases b Particles in a REAL gas… have their own volume attract each other b Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

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C. Characteristics of Gases b Gases expand to fill any container. random motion, no attraction b Gases are fluids (like liquids). no attraction b Gases have very low densities. no volume = lots of empty space

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C. Characteristics of Gases b Gases can be compressed. no volume = lots of empty space b Gases undergo diffusion & effusion. random motion

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D. Temperature ºF ºC K -45932212 -2730100 0273373 K = ºC + 273 b Always use absolute temperature (Kelvin) when working with gases.

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E. Pressure Which shoes create the most pressure?

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E. Pressure b Barometer measures atmospheric pressure Mercury Barometer Aneroid Barometer

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E. Pressure b Manometer measures contained gas pressure U-tube ManometerBourdon-tube gauge

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E. Pressure b KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

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F. STP Standard Temperature & Pressure 0°C 273 K 1 atm101.325 kPa -OR- STP

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II. The Gas Laws BOYLES CHARLES GAY- LUSSAC Ch. 12 - Gases

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A. Boyles Law P V PV = k

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A. Boyles Law b The pressure and volume of a gas are inversely related at constant mass & temp P V PV = k

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A. Boyles Law

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V T B. Charles Law

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V T b The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure

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B. Charles Law

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GIVEN: V 1 = 473 cm 3 T 1 = 36°C = 309K V 2 = ? T 2 = 94°C = 367K WORK: P 1 V 1 T 2 = P 2 V 2 T 1 E. Gas Law Problems b A gas occupies 473 cm 3 at 36°C. Find its volume at 94°C. CHARLES LAW T V (473 cm 3 )(367 K)=V 2 (309 K) V 2 = 562 cm 3

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GIVEN: V 1 = 100. mL P 1 = 150. kPa V 2 = ? P 2 = 200. kPa WORK: P 1 V 1 T 2 = P 2 V 2 T 1 E. Gas Law Problems b A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa. BOYLES LAW P V (150.kPa)(100.mL)=(200.kPa)V 2 V 2 = 75.0 mL

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III. Ideal Gas Law Gases

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V n A. Avogadros Principle

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V n b Equal volumes of gases contain equal numbers of moles at constant temp & pressure true for any gas

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PV T VnVn PV nT B. Ideal Gas Law = k UNIVERSAL GAS CONSTANT R=0.0821 L atm/mol K R=8.315 dm 3 kPa/mol K = R

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B. Ideal Gas Law UNIVERSAL GAS CONSTANT R=0.0821 L atm/mol K R=8.315 dm 3 kPa/mol K PV=nRT

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GIVEN: P = ? atm n = 0.412 mol T = 16°C = 289 K V = 3.25 L R = 0.0821 L atm/mol K WORK: PV = nRT P(3.25)=(0.412)(0.0821)(289) L mol L atm/mol K K P = 3.01 atm B. Ideal Gas Law b Calculate the pressure in atmospheres of 0.412 mol of He at 16°C & occupying 3.25 L. IDEAL GAS LAW

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GIVEN: V = ?V = ? n = 85 g T = 25°C = 298 K P = 104.5 kPa R = 8.315 dm 3 kPa/mol K B. Ideal Gas Law b Find the volume of 85 g of O 2 at 25°C and 104.5 kPa. = 2.7 mol WORK: 85 g 1 mol = 2.7 mol 32.00 g PV = nRT (104.5)V=(2.7) (8.315) (298) kPa mol dm 3 kPa/mol K K V = 64 dm 3 IDEAL GAS LAW

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WORK: PV = nRT (97.3 kPa) (15.0 L) = n (8.315 dm 3 kPa/mol K ) (294K) n = 0.597 mol O 2 B. Gas Stoichiometry Problem b How many grams of Al 2 O 3 are formed from 15.0 L of O 2 at 97.3 kPa & 21°C? GIVEN: P = 97.3 kPa V = 15.0 L n = ?n = ? T = 21°C = 294 K R = 8.315 dm 3 kPa/mol K 4 Al + 3 O 2 2 Al 2 O 3 15.0 L non-STP ? g Given liters: Start with Ideal Gas Law and calculate moles of O 2. NEXT

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2 mol Al 2 O 3 3 mol O 2 B. Gas Stoichiometry Problem b How many grams of Al 2 O 3 are formed from 15.0 L of O 2 at 97.3 kPa & 21°C? 0.597 mol O 2 = 40.6 g Al 2 O 3 4 Al + 3 O 2 2 Al 2 O 3 101.96 g Al 2 O 3 1 mol Al 2 O 3 15.0L non-STP ? g Use stoich to convert moles of O 2 to grams Al 2 O 3.

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A. Daltons Law b The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases. P total = P 1 + P 2 +... P atm = P H2 + P H2O

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GIVEN: P H2 = ? P total = 94.4 kPa P H2O = 2.72 kPa WORK: P total = P H2 + P H2O 94.4 kPa = P H2 + 2.72 kPa P H2 = 91.7 kPa A. Daltons Law b Hydrogen gas is collected over water at 22.5°C. Find the pressure of the dry gas if the atmospheric pressure is 94.4 kPa. Look up water-vapor pressure on p.899 for 22.5°C. Sig Figs: Round to least number of decimal places. The total pressure in the collection bottle is equal to atmospheric pressure and is a mixture of H 2 and water vapor.

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GIVEN: P gas = ? P total = 742.0 torr P H2O = 42.2 torr WORK: P total = P gas + P H2O 742.0 torr = P H2 + 42.2 torr P gas = 699.8 torr b A gas is collected over water at a temp of 35.0°C when the barometric pressure is 742.0 torr. What is the partial pressure of the dry gas? DALTONS LAW Look up water-vapor pressure on p.899 for 35.0°C. Sig Figs: Round to least number of decimal places. A. Daltons Law The total pressure in the collection bottle is equal to barometric pressure and is a mixture of the gas and water vapor.

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