CHEG 200: Chemical Engineering Principles
Study Guide for Final Exam
Energy Balances without chemical reaction
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Select an appropriate form for the energy balance, either based on mass or mole.
Write the general form of the energy balance for either an open or closed system.
Apply assumptions like negligible changes in kinetic and potential energy, no reactions, adiabatic,
and no shaft work to simplify this general form.
Define the terms flow work and specific internal energy, volume, and enthalpy.
Write the specific enthalpy of any process stream (or material) in general form as a function of
temperature, pressure, and composition {i.e., H = hmix[T, P, comp]}.
Sketch the PH and PU diagrams for a typical pure component and choose its reference state.
Identify the single phases and equilibrium phases in these diagrams.
Trace a multi-step process in both diagrams.
Label each diagram with tabular data from the literature, such as melting point, boiling point, critical
point, saturated liquid and vapor molar or specific quantities.
Apply the reverse-lever rule in the two-phase regions of these diagrams.
Compare the tabular data in the steam tables to the PH and PU diagrams.
Analyze energy balance problems using a PH diagram or tabular PH or PU data.
Calculate the molar or specific enthalpy of multi-component process stream for an ideal solution (i.e.,
mixture is equal to sum of its pure components).
Select a reference state (T, P, and stable phase) for a pure component, and calculate sensible and
latent heat changes that go from the reference state to the state of the process stream.
Derive why the reference state of a pure component can be arbitrarily selected for non-reacting
system.
Calculate the molar or specific enthalpy of a process stream for a non-ideal mixture.
Analyze material and energy balance problems that require the mixture enthalpies be calculated by a
set of equations.
Solve material and energy balance problems that require the use of an HXY diagram.
Energy Balances with chemical reaction
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Select the reference state as the pure elements (i.e., atoms) at 25ºC, 1 atm, and stable phase of the
elements.
Calculate mixture enthalpies of process streams starting with this reference state; that is, the standard
heat of formation to create the compound from the elements.
Calculate the standard heat of a reaction and identify if it is endo- or exo-thermic.
Classify the operation of a reactor as isothermal, adiabatic, non-isothermal, or non-adiabatic.
Analyze energy balance problems using the heat-of-formation method (i.e., energy balance contains
no heat-of-reaction term and mixture enthalpy calculations begin with the standard heat of formation
of the components).
Analyze energy balance problems using the heat-of-reaction method (i.e., energy balance is written
with a heat-of-reaction term and mixture enthalpy calculations do not contain the standard heat of
formation of the components).
Derive the heat-of-reaction method starting with the heat-of-formation method.
Compare and contrast these two forms of the energy balance.
Final Exam Study Guide
Page 1 of 2
Michael Hanyak
CHEG 200: Chemical Engineering Principles
Study Guide for Final Exam
Energy Balance Analysis
a. Differential Energy Balance
energy unit/time {
continuous process }
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blue crib sheet for no chemical reactions; pink crib sheet for chemical reactions
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hmix [ temperature, pressure, composition ]
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hmix functional form:
for each process stream
graph, table, equation(s), or computer program
If hmix is for a pure substance, use Hˆ j function on appropriate crib sheet (Item D.7).
If hmix is for a mixture, use a graph when it is provided for the mixture.
If hmix is for a mixture, use a table when it is provided for the mixture.
If hmix is for a mixture, use enthalpy equation on appropriate crib sheet (Items C and D).
If hmix is for a mixture, use Aspen HYSYS for assigned project problems.
b. Integral Energy Balance
energy units only
{ batch, semi-batch, or continuous process }
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blue crib sheet for no chemical reactions; pink crib sheet for chemical reactions
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hmix [ temperature, pressure, composition ]
for each process stream
graph, table, equation(s), or computer program
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umix [ temperature, pressure, composition ]
(see hmix function above)
for final and initial state of system
If umix is for pure water, use steam tables (B.5, B.6, and B.7) for UˆWA .
If umix is for a pure substance other than pure water, then do one of the following:
For a solid or liquid,
For an ideal gas,
For real gas,
Uˆ j  Uˆ j T j , Pj , Ph j  
Uˆ j  Uˆ j T j , Pj , Ph j  

T
Tj
 Cˆ
T
Tj
Cˆ PPh, ji dT
ig
P, j
with Uˆ j  0

 R dT with Uˆ j  0
use Aspen HYSYS to find Uˆ j of pure substance j.
If umix is for a mixture, use a graph when it is provided for the mixture.
If umix is for a mixture, use a table when it is provided for the mixture.
If umix is for a mixture, use Items C and D on a crib sheet with Uˆ in place of Hˆ .
If umix is for a mixture, use Aspen HYSYS for assigned project problems.
Any functional form [ … ]: graph, table, equation(s), or computer program.
Final Exam Study Guide
Page 2 of 2
Michael Hanyak