Dead Week Review:
Material Balances
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
German Parada
ChE 210
Lamm/Scheider
12/03/2012
Conceptual Questions:
1) What kind of information do you NEED to include in a fully-labeled flowchart? What
kind of information you DON’T want to put in a flowchart?
2) You are teaching an incoming ChE student how to carry out a DoF analysis. Explain how
to do a DoF when:
a. The is no chemical reactions in the system
b. There is a chemical reaction, and you want to use the molecular balance method
Short Problem:
1) Acetaldehyde (C2H4O) decomposition at high temperatures is a complicated reaction that
produces methane (CH4), carbon dioxide (CO2), carbon monoxide (CO) and water
(H2O). Ten moles of acetaldehyde are reacted to completion in a closed vessel, and half a
mol of water was obtained. Find the ratio of CO to CO2 produced.
Engineering Problems:
1) Propyl benzoate (PB) is a compound that has a nutty smell and flavor, and it used in the
food industry for artificial flavoring. This compound is obtained by reacting benzoic acid
(BA) and propanol (P) in the reaction shown below.
The PB is then extracted with hexane (H) from the aqueous stream leaving the reactor.
You are in charge of the PB production, and have been asked by your supervisor to check
the amount of hexane used for the extraction. In the unit, the reactor is fed with 150
mol/min of BA and propanol in 20% excess. The fractional conversion of the reactor is
85%. In the extraction unit, a
certain amount of pure H is fed,
and the PB partitions between the
aqueous and organic streams, with
a K of 20 (mol PB in the organic
phase/mol PB in the aqueous
phase). The concentration of PB in
the exiting organic stream is 25%.
How much hexane is being used by
this unit?
Supplemental Instruction
1060 Hixson-Lied Student Success Center  294-6624  www.si.iastate.edu