University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |1
1. A pure substance has a specific volume of 0.08 L/mol at a pressure of 3 atm
and 298 K. The substance is most likely:
a.
b.
c.
d.
Liquid
Gas
Supercritical Fluid
Vapor
2. A rigid tank contains CO2 at 2 atm and 50°C. When the tank is heated to 250°C,
the pressure increases significantly and the gas density…
a.
b.
c.
d.
Increases
Decreases
Remains the Same
Tank Explodes
3. Two pathways are shown from points 1 to 2 on the pressure-temperature
diagram. One pathway has a phase change (dashed line) and the other does
not (solid lines). Which pathway has the larger change in enthalpy?
a.
b.
c.
d.
Solid
Dashed
Same for Both
No Way to
Know
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |2
4. Which line corresponds to an
isotherm for a gas?
5. A fluid flows steadily through a circular pipe of uniform cross-sectional area as
shown below.
If the outlet density of the fluid decreases to 1/2 of its inlet value, what
happens to the average fluid velocity?
a. The velocity will not change since mass must be conserved and the flow
is steady-state.
b. The outlet velocity will be 1/4th of the inlet velocity since kinetic energy
must be conserved according to the Bernoulli equation.
c. The outlet velocity will be twice the inlet velocity since mass must be
conserved in the system.
d. The velocity will increase somewhat but we can’t tell how much with the
information given.
e. The velocity will decrease somewhat because of friction between fluid
and the pipe wall.
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |3
6. A wastewater treatment process requires 100 cubic feet per minute (CFM) of
air at STP in order to meet the oxygen demand of the microorganisms. The
actual volumetric flowrate of air needed to meet this demand on a winter day
(0 oC) in Denver, CO (Patm = 0.83 atm) would be ________________.
a.
b.
c.
d.
less than 100 CFM
exactly 100 CFM
greater 100 CFM
can't say without more information
7. Consider two vapor mixtures of saturated water in air. One is at 20 oC and 1
atm and the other is at 20 oC and 2 atm. Which one has a higher partial
pressure of water?
a.
b.
c.
d.
The mixture at 20 oC and 1 atm
The mixture at 20 oC and 2 atm
The same in both mixtures
You cannot tell
8. A chemist filled a 1 L flask with ethanol (specific gravity = 0.79) in 20 seconds
through a funnel. The time to fill the same flask with water if the mass flow
rate is the same would be ________.
a.
b.
c.
d.
Shorter
Longer
Same
Can’t Tell
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |4
9. Propane (C3H8) reacts with oxygen to form carbon dioxide and water
C3H8 + 5O2 --> 4H2O + 3CO2
If 50 moles C3H8 enters a reactor with 50 moles O2, and assuming full
conversion of the limiting reactant, how many moles of H2O form?
a.
b.
c.
d.
200 mols
40 mols
50 mols
30 mols
10. Ammonia is compressed isothermally at 300 K until liquid NH3 forms at
pressure Pa. In a second container, ammonia is compressed at 350 K until it
condenses at a pressure Pb. The pressure Pa is __________ Pb.
a.
b.
c.
d.
greater than
less than
equal to
no way to know
11. A sealed container contains water and air. At 100°C, the system is saturated
with water, which makes up 25% of the vapor. What is the pressure of the
system?
a.
b.
c.
d.
1 bar
0.25 bar
4 bar
10 bar
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |5
12. A fixed-volume container at 45°C contains 1 L of
liquid benzene and 1 L of benzene vapor in
equilibrium. If 0.4 L liquid benzene is removed at
constant temperature, the benzene partial
pressure ____________.
a.
b.
c.
d.
increases
decreases
remains the same
not enough information
13. We want to separate a 50/50 mixture of C6 isomers in the gas phase. As the
temperature is lowered, a technician states that he observed that some nhexane (n-C6) condenses before any 2,2- dimethylbutane (DMB) condenses.
Does this actually happen?
a.
b.
c.
d.
Yes, if n-C6 has a lower vapor pressure than DMB.
Yes, if n-C6 has a higher vapor pressure than DMB.
No, because both species have to condense.
It depends on the system pressure as to whether one or two species
condense.
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |6
14. A cooling crystallizer operates at 30°C to form salt crystals from a solution of
dissolved salt in water. 100 g of solution enters the crystallizer at 100°C. The
crystallizer extracts 25 g
of salt. What is the mass
fraction of salt in the exit
stream?
a.
b.
c.
d.
0.20
0.25
0.33
0.50
15. 1 lbm of H2SO4 at 60°F is added to
enough water at 60°F to make a
25 wt% solution in an adiabatic
vessel. What is the final
temperature of the mixture?
a.
b.
c.
d.
60°F
100°F
160°F
> 200°F
University of Alabama Chemical & Biological Engineering - CHE 305-001 Fall 2014
Name:
September 19, 2014 EXAM 1
Page |7
16. A small tank contains dry air at 25°C. A small
beaker of water at 25°C is placed in the container,
which is then sealed. The tank is well insulated.
When equilibrium is reached, the air temperature
is __________.
a.
b.
c.
d.
slightly higher
slightly lower
the same
can’t tell