Gas Mixtures and Partial Pressures

Gas Mixtures and Partial Pressures - And so on for all...

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Gas Mixtures and Partial Pressures How do we deal with gases composed of a mixture of two or more different substances? John Dalton (1766-1844) - (gave us Dalton's atomic theory ) The total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone The partial pressure of a gas: The pressure exerted by a particular component of a mixture of gases Dalton's Law of Partial Pressures: P t is the total pressure of a sample which contains a mixture of gases P 1 , P 2 , P 3 , etc. are the partial pressures of the gases in the mixture P t = P 1 + P 2 + P 3 + . .. If each of the gases behaves independently of the others then we can apply the ideal gas law to each gas component in the sample: For the first component, n 1 = the number of moles of component #1 in the sample The pressure due to component #1 would be: For the second component, n 2 = the number of moles of component #2 in the sample The pressure due to component #2 would be:
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Unformatted text preview: And so on for all components. Therefore, the total pressure P t will be equal to: All components will share the same temperature, T , and volume V , therefore, the total pressure P t will be: Since the sum of the number of moles of each component gas equals the total number of moles of gas molecules in the sample: At constant temperature and volume, the total pressure of a gas sample is determined by the total number of moles of gas present, whether this represents a single substance, or a mixture Example A gaseous mixture made from 10 g of oxygen and 5 g of methane is placed in a 10 L vessel at 25C. What is the partial pressure of each gas, and what is the total pressure in the vessel? (10 g O 2 )(1 mol/32 g) = 0.313 mol O 2 (10 g CH 4 )(1 mol/16 g) = 0.616 mol CH 4 V=10 L T=(273+25K)=298K P t = P O2 + P CH4 = 0.702 atm + 1.403 atm = 2.105 atm...
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Gas Mixtures and Partial Pressures - And so on for all...

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