23 General Chemistry: Chapter 6 Chemistry 140 Fall 2008Example 6-4, Molar Mass with the Ideal Gas EquationExample 5-6Use the Ideal Gas Equation:PV =mMRTM =mPVRTPV = nRTP = 740.3/760 * kPaM =(P kPa)( dm3)( g)( J mol-1 K-1)(297.2 K)This gas must be ketene. There really are no other possibilities.[Pa · m3] = [kPa · dm3] = [J]M = g · mol-1General Chemistry: Chapter 6
31 Partial pressure and volume Chemistry 140 Fall 2008Partial pressure and volumePtot = Pa + Pb +…Va = naRT/Ptot and Vtot = Va + Vb+…VaVtotnaRT/PtotntotRT/Ptot=nantotnantot=xaRecallPartial pressure is the pressure of a component of gas that contributes to the overall pressure.Partial volume is the volume that a gas would occupy at the total pressure in the chamber.Ratio of partial volume to total volume, or of partial pressure to total pressure is the MOLE FRACTION.PaPtotnaRT/VtotntotRT/Vtot=nantotGeneral Chemistry: Chapter 6
32 Average molar mass of ideal gas mixtures The average molar mass is a sum of the products of the components molar fractions (xi) and masses (Mi).