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 Spring 2003/2004

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

3. R =PV/nT at standard conditions Standard conditions are:
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 Spring 2003/2004

4. For a gas changing from state 1 to state 2: P1 V1=n1RT1 (1) and
THE IDEAL GAS LAW
For a gas changing from state 1 to state 2:
P1 V1=n1RT (1) and
P2 V2=n2RT (2)
Divide equation 1 by equation 2
P2 V n2T2
P1 V n1T1 =
Dr. F. Iskanderani ChE Spring 2003/2004

5. GAS Density: is mass/Volume V (PV=nRT Thus n/V =P/RT)
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
 of gas at specified conditions
 of air at specified conditions
specific gravity =
of a gas
Dr. F. Iskanderani ChE Spring 2003/2004

6. a- Dalton's Law (of partial pressures)
2) Ideal Gas Mixtures
a- Dalton's Law (of partial pressures)
N2 gas
H2 gas
O2 gas
O 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
ptotal V ntotal RT
pi V ni RT =
Dr. F. Iskanderani ChE Spring 2003/2004

7. pi = ptot ni/ntot = ptot x yi
THUS p1+p2+p = 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 the same volume occupied by the mixture at the same T of the mixture.
Dr. F. Iskanderani ChE Spring 2003/2004

8. b- Amagat's Law (of partial volumes) P is fixed. T is fixed
N2 gas
H2 gas
O2 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 Spring 2003/2004

9. Vi = Vtot ni/ntot = Vtot x yi
P Vtotal ntotal RT
P Vi ni RT =
Vi = Vtot ni/ntot = Vtot x yi
THUS V1+V2+V = 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 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 Spring 2003/2004

11. Material balance involving gases: Example1: Find F in m3/min
m3/min of CO2 at 7oC and 131 KPa A
Vol%
CO2
3.4
Others
96.6
100%
Vol%
CO2
1.2
Others
98.8
100% F P
At 15oC and 105 KPa
At 15oC and 105 KPa
Dr. F. Iskanderani ChE Spring 2003/2004

12. 40% excess Air at 70oF and 29.4 in Hg
Example 2: 10% of CO does not burn. Find the ft3 of air supplied per ft3 of entering gas. Find the ft3 of flue gas at given conditions per ft3 of entering gas
40% excess Air at 70oF and 29.4 in Hg
CO2 O2 CO
H2O N2
Mole %
CO2
6.4 O2
0.1 CO
39.0 H2
51.5
CH4
0.6 N2
2.1
COMBUSTION CHAMBER
At 400oF and 29.4 in Hg
At 90oF and 35 in Hg