CHE200 - Chemical Eng Fundamentals
Chapter 4 Material Balances:
Material balances are nothing than the application of the
“CONSERVATION LAW FOR MASS”:
Mass is neither created nor destroyed.
Balances on reactive processes
1. Molecular species balances on reactive processes are often
cumbersome. They must include gene ration and consumption terms
for each species and one degree of freedom must be added for each
independent reaction.
2. Atomic species balances have the simple form input = output and
are usually more straightforward than either of the other methods.
3. Extent of reaction are particularly convenient for reaction
equilibrium calculations.
Molecular species balances
If molecular species balances are used for a reactive process, the balances
on reactive species must contain generation and/or consumption terms.
The degree-of-freedom analysis is as follows:
No. unknown labeled variables
+ No. independent chemical reactions
- No. independent molecular species balances
- No. other equations relating unknown variables
= No. degrees of freedom
Atomic species balances
All balances on atomic species take the form “input = output”, since atomic
species can neither be generated nor consumed in chemical reactions.
The degree-of-freedom analysis:
No. unknown labeled variables
- No. independent atomic species balances
- No. molecular balances on independent non-reactive species
Chapter 4 Material Balances:
Material balances are nothing than the application of the
“CONSERVATION LAW FOR MASS”:
Mass is neither created nor destroyed.
Balances on reactive processes
1. Molecular species balances on reactive processes are often
cumbersome. They must include gene ration and consumption terms
for each species and one degree of freedom must be added for each
independent reaction.
2. Atomic species balances have the simple form input = output and
are usually more straightforward than either of the other methods.
3. Extent of reaction are particularly convenient for reaction
equilibrium calculations.
Molecular species balances
If molecular species balances are used for a reactive process, the balances
on reactive species must contain generation and/or consumption terms.
The degree-of-freedom analysis is as follows:
No. unknown labeled variables
+ No. independent chemical reactions
- No. independent molecular species balances
- No. other equations relating unknown variables
= No. degrees of freedom
Atomic species balances
All balances on atomic species take the form “input = output”, since atomic
species can neither be generated nor consumed in chemical reactions.
The degree-of-freedom analysis:
No. unknown labeled variables
- No. independent atomic species balances
- No. molecular balances on independent non-reactive species
