Presentation on theme: "Ideal Gas Law & Dalton’s Law"— Presentation transcript:
1 Ideal Gas Law & Dalton’s Law Ch. 12 & 13 - GasesIII. Two More LawsIdeal Gas Law & Dalton’s Law
2 A. Avogadro’s Principle Equal volumes of gases contain equal numbers of molesat constant temp & pressuretrue for any gasVn
3 UNIVERSAL GAS CONSTANT B. Ideal Gas LawMerge the Combined Gas Law with Avogadro’s Principle:PVTPVnTVn= k= RUNIVERSAL GAS CONSTANTR= Latm/molKR=8.315 dm3kPa/molKYou don’t need to memorize these values!
4 UNIVERSAL GAS CONSTANT B. Ideal Gas LawPV=nRTUNIVERSAL GAS CONSTANTR= Latm/molKR=8.315 dm3kPa/molKYou don’t need to memorize these values!
5 C. Ideal Gas Law Problems Calculate the pressure in atmospheres of mol of He at 16°C & occupying L.GIVEN:P = ? atmn = molT = 16°C = 289 KV = 3.25 LR = Latm/molKWORK:PV = nRTP(3.25)=(0.412)(0.0821)(289)L mol Latm/molK KP = 3.01 atm
6 C. Ideal Gas Law Problems Find the volume of 85 g of O2 at 25°C and kPa.GIVEN:V = ?n = 85 gT = 25°C = 298 KP = kPaR = dm3kPa/molKWORK:85 g 1 mol = 2.7 mol32.00 g= 2.7 molPV = nRT(104.5)V=(2.7) (8.315) (298)kPa mol dm3kPa/molK KV = 64 dm3
7 Ptotal = P1 + P2 + ... D. Dalton’s Law The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases.Ptotal = P1 + P
8 D. Dalton’s Law GIVEN: PO2 = ? Ptotal = 1 atm PCO2 = 0.285 torr Three of the primary components of air are CO2, N2, and O2. In a sample containing only these three gases at a pressure of 1.00 atm, PCO2 = torr and PN2 = torr. What is the partial pressure of O2?GIVEN:PO2 = ?Ptotal = 1 atmPCO2 = torrPN2 = torrWORK:Ptotal = PCO2 + PN2 + PO21 atm = atm atm + PO2PO2 = atm= atm= atm
9 Patm = Pgas + PH2O D. Dalton’s Law When H2 gas is collected by water displacement, the gas in the collection bottle is actually a mixture of H2 and water vapor.Water exerts a pressure known as water-vapor pressureSo, to determine total pressure of gas and water vapor inside a container, make total pressure inside bottle = atmosphere and use this formula:Patm = Pgas + PH2O
10 D. Dalton’s LawHydrogen gas is collected over water at 22.5°C. Find the pressure of the dry gas if the atmospheric pressure is 94.4 kPa.The total pressure in the collection bottle is equal to atmospheric pressure and is a mixture of H2 and water vapor.GIVEN:PH2 = ?Ptotal = 94.4 kPaPH2O = 2.72 kPaWORK:Ptotal = PH2 + PH2O94.4 kPa = PH kPaPH2 = 91.7 kPaLook up water-vapor pressure on p.899 for 22.5°C.Sig Figs: Round to least number of decimal places.
11 D. Dalton’s Law GIVEN: Pgas = ? Ptotal = 742.0 torr PH2O = 42.2 torr A gas is collected over water at a temp of 35.0°C when the barometric pressure is torr. What is the partial pressure of the dry gas?The total pressure in the collection bottle is equal to barometric pressure and is a mixture of the “gas” and water vapor.GIVEN:Pgas = ?Ptotal = torrPH2O = 42.2 torrWORK:Ptotal = Pgas + PH2O742.0 torr = PH torrPgas = 700. torrLook up water-vapor pressure on p.899 for 35.0°C.Sig Figs: Round to least number of decimal places.
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