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Gases, Vapors, Liquids, and Solids

Gases, Vapors, Liquids, and Solids As Engineers, we face processes, operations that require knowledge of properties; such as : P, T, V, (these can be measured) H,U,S, (these are calculated from measured ones) Some Data for properties of pure substances and mixtures are available

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Gases, Vapors, Liquids, and Solids

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  1. Gases, Vapors, Liquids, and Solids As Engineers, we face processes, operations that require knowledge of properties; such as : P, T, V, (these can be measured) H,U,S, (these are calculated from measured ones) Some Data for properties of pure substances and mixtures are available But not all data are available Dr. F. Iskanderani ChE 201 Spring 2003/2004

  2. => we need to predict the data required. • Predictions: • some predictions have theoretical background • some are empirical Dr. F. Iskanderani ChE 201 Spring 2003/2004

  3. THE IDEAL GAS LAW 1) For pure substances PV=nRT R can be calculated : R =PV/nT at standard conditions Standard conditions are: P=1atm,n =1kg mole, T=273.15°K; V=22.415m3 Any equivalent units can be used to generate an R value at these units Dr. F. Iskanderani ChE 201 Spring 2003/2004

  4. P1 V1 n1T1 = P2 V2 n2T2 THE IDEAL GAS LAW For a gas changing from state 1 to state 2: P1 V1=n1RT1 (1) and P2 V2=n2RT2 (2) Divide equation 1 by equation 2 Dr. F. Iskanderani ChE 201 Spring 2003/2004

  5.  of gas at specified conditions specific gravity = of a gas  of air at specified conditions THE IDEAL GAS LAW GAS Density: is mass/Volume n=m/Mwt =>  = m/V= n x Mwt V (PV=nRT Thus n/V =P/RT) Therefore : =P x MWt RT Dr. F. Iskanderani ChE 201 Spring 2003/2004

  6. pi Vni RT = ptotal Vntotal RT 2) Ideal Gas Mixtures a- Dalton's Law (of partial pressures) N2 gas H2 gas O2 gas O2 + N2 + H2 V is fixed V is fixed V is fixed V is fixed pN2 V = nN2RT pH2 V = nH2RT pO2 V = nO2RT ptot V = ntotRT Or in general: pi V = niRT Dr. F. Iskanderani ChE 201 Spring 2003/2004

  7. pi = ptot ni/ntot = ptotx yi THUS p1+p2+p3+ .. + .. = ptot(y1+ y2 +y3 +..) = ptot PARTIAL PRESSURE: Pressure that would be exerted by a single component in a gaseous mixture if it existed alone in thesame volumeoccupied by the mixtureat the same T of the mixture. Dr. F. Iskanderani ChE 201 Spring 2003/2004

  8. P P P P b- Amagat's Law (of partial volumes) P is fixed. T is fixed O2 gas N2 gas H2 gas O2 + N2 + H2 V is variable P VN2 = nN2RT P VH2 = nH2RT P VO2 = nO2RT P Vtot = ntotRT Or in general: P Vi = niRT Dr. F. Iskanderani ChE 201 Spring 2003/2004

  9. P Vini RT = P Vtotalntotal RT Vi = Vtot ni/ntot = Vtotx yi THUS V1+V2+V3+ .. + .. = Vtot(y1+ y2 +y3 +..) = Vtot PARTIAL VOLUME: Volume that would be occupied by a single component in a gaseous mixture if it is put alone under the same (total) pressure of the mixture at the same T of the mixture. Dr. F. Iskanderani ChE 201 Spring 2003/2004

  10. Example: A gas mixture contains 14% CO2, 6%O2 and 80% N2 at 400oF and 750 mmHg. Calculate the partial pressure of each component. If the total volume of container is 2 ft3, calculate the partial volume of each component. Dr. F. Iskanderani ChE 201 Spring 2003/2004

  11. Material balance involving gases: Example1: Find F in m3/min 0.0917 m3/min of CO2 at 7oC and 131 KPa A F P At 15oC and 105 KPa At 15oC and 105 KPa Dr. F. Iskanderani ChE 201 Spring 2003/2004

  12. Example 2: 10% of CO does not burn. Find the ft3 of air supplied per ft3 of entering gas. Find the ft3 offlue gas at given conditions per ft3 of entering gas 40% excess Air at 70oF and 29.4 in Hg COMBUSTION CHAMBER At 400oF and 29.4 in Hg At 90oF and 35 in Hg

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