Dalton\'s law states that the pressure, Ptotal, of a mixture of gases in a conta
ID: 749453 • Letter: D
Question
Dalton's law states that the pressure, Ptotal, of a mixture of gases in a container equals the sum of the pressures of each individual gas: Ptotal = P1 + P2 + P3 + . . .. The partial pressure of the first component, P1, is equal to the mole fraction of this component, Z1, times the total the total pressure of the mixture: P1 = X1 times Ptotal The mole fraction, X, represents the concentration of the component in the gas mixture, so X1 = moles of component 1/total moles in mixture Part A Three gases (8.00 g of methane, CH4, 18.0 g of ethane, C2H6, and an unknown amount of propane, C3H8) were added to the same 10.0-L container. At 23.0 degree C, the total pressure in the container is 4.00atm. Calculate the partial pressure of each gas in the container. Express the pressure values numerically in atmospheres, separated by commas. Enter the partial pressure of methane first, then ethane, then propane. Part B A gaseous mixture of O2 and N2 contains 35.8% nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 405mmHg ? Express you answer numerically in millimeters of mercury.Explanation / Answer
Assuming it behaves an ideal gas. PV = nRT ....///..... total moles (n) = PV / RT............. = (4)(10) / (0.08205) (273.15 + 23) =1.645 moles............... moles of methane = 8 / 16 = 0.5 mole and moles of ethane = 18 / 30 = 0.225 mole and mole propane = 1.645 - 0.5 - 0.225 = 0.92 mole............... mole fraction = pressure fraction:....... methane = 0.5 / 1.645 = 0.304.............. Ethane = 0.225 / 1.645 = 0.1367........... Propane = 0.92 / 1.645 = 0.5592.............. partial pressure = mole fraction x total pressure assume 100 g mixture.. 64.2% = .... oxygen = 64.2% = 64.2 g and nitrogen = 35.8% = 35.8 g ............... mw O2 = 32 g/mole....................... mw N2 = 28 g/mole........................ moles O2 = 64.2/32 = 2.01 moles............................... moles N2 = 35.8/28 = 1.28 moles................................. mole fraction O2 = 2.01/ (2.01+1.28) = 0.611..................... so partial pressure O2 = 0.611 x 405 mmHg = 247.455 mmHg
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