HW Set 2

Name(s) (up to three students per homework set):
Due:
In class, Friday
February 7, 2014
Section number(s)
1.
2.
3.
M E 433
Spring Semester, 2014
Homework Set # 2
Professor J. M. Cimbala
1.
2.
3.
4.
For instructor or TA use only:
Problem
Score
Points
1
15
2
20
3
10
4
10
5
15
6
30
Total:
100
(15 pts) Methyl chloroform reacts with gaseous oxygen to form carbon dioxide and hydrogen chloride. Write out the
stoichiometric equation for this chemical reaction. For consistency, please use 1 as the stoichiometric coefficient for the
methyl chloroform in your chemical reaction equation.
(20 pts) Read Section II of Chapter 1 in the textbook. Pay particular attention to the numerical values of the sulfur
dioxide levels and particulate levels in the air during the Donora and London disasters.
(a) Look up Air Quality Index (AQI) on the Internet, and print out or write a table that lists the AQI index and what it
means. Look specifically for the minimum particulate level of PM10 particles that EPA considers “unhealthy for
sensitive groups.” What particle concentration (in units of mg/m3) is considered unhealthy for sensitive groups (i.e., the
maximum concentration that is still considered “moderately healthy”? List your source(s).
(b) Based on your answer from Part (a), verify the statement on page 6 of the text that says the Donora air had 200 times
the limit for PM10 particles. In other words, explain and verify how the authors came up with this value of 200. Using
the same kind of math, by what factor did the air in London, 1952 exceed the PM10 maximum healthy limit?
(c) Compare the AQI for PM10 particles with the NAAQS level (See page 150 of Phalen & Phalen). Are they the same?
Discuss.
(d) Now consider the gaseous pollutant, sulfur dioxide (SO2), and the levels reported in the textbook for both of these
events. Compare these to the OSHA TWA-PEL for SO2 gas. Note: OSHA TWA-PEL is an 8-hour time-weighted
average permissible exposure level. For proper comparison, since people in these cities were exposed all day, divide the
TWA-PEL by 3 (24 hours / 8 hours) to estimate the maximum permissible level of SO2 in the air. Compare to the actual
reported levels in the two cities and discuss whether sulfur dioxide or particulate matter were most likely the main cause
of deaths in those incidents.
(e) Finally, compare the OSHA TWA-PEL for sulfur dioxide with the NAAQS level (See page 150 of Phalen & Phalen).
Are they the same? Discuss. Specifically, if one of them is much higher than the other, discuss why.
(10 pts) As I mentioned on the first day of class, my main complaint about our textbook is that it is too qualitative rather
than quantitative. As an example, Table 2-2 lists conversion factors for converting from mass concentration to volume
fraction, but these apply only at STP (25oC and 1 atm pressure).
(a) Using the more general conversion equation given in class, verify that the equation given in Table 2-2 for conversion
factor k is correct. Be careful to list and apply all units and unit conversions correctly.
(b) Let’s pick sulfur dioxide as a test case since you already should have looked up its MSDS in the previous problem. The
MSDS also lists a conversion factor, which is also valid only at STP. Verify that the conversion factor listed in the
MSDS is the same as that listed in Table 2-2 for sulfur dioxide.
(10 pts) Consider Table 2-3 in the textbook. They list PPM values for the various components of standard air for both dry
air (0% relative humidity) and wet air (100% relative humidity).
(a) Considering our class discussions about relative humidity, show how they came up with the ppm by volume value
(31,200 PPM) for the wet air case. Show all your work and explain.
(b) Is “wet air” less dense or more dense than “dry air”? Explain and justify.
Note: There is another page. 
5.
6.
(15 pts) In class we listed four major greenhouse gases: H2O, CO2, CH4, and N2O. Consider the last one listed, nitrous
oxide.
(a) Do some Internet searching; what is the approximate ratio of impact per unit mass of N2O compared to CO2 as
greenhouse gases? Rank the four gases in terms of greenhouse impact and discuss. Be sure to reference your source(s).
(b) Search for plots of the increase of CO2, CH4, and N2O in the atmosphere for the past several decades. Show the plots
and compare the relative concentrations of the three chemicals in the air at the present time.
(30 pts) Consider a sample of humid air as an ideal gas mixture that consists of the following gases, in percent by volume:
O2 (20.0%), N2 (75.0%), H2O (4.96%), and CO2 (0.04%). The gas mixture is at a total pressure of 95.4 kPa, and the
temperature is 35.0oC. Note: To calculate the molecular weight of each molecule, use data from the on-line periodic chart on
the course website for greatest accuracy and consistency. I suggest that you use Excel to avoid calculation errors, and for
neatness; Excel is very useful for these kinds of repetitive calculations with summations, etc.
(a) Calculate the mol fraction of each species, both as a unitless number and in “units” of PPM. Verify that yj = 1, and
yj,PPM = 1000000.
(b) Calculate the partial pressure of each species in kPa. Verify that Pj = P.
(c) Calculate the mass fraction of each species. Verify that fj = 1.
(d) Calculate the mass concentration (cj) of each species in mg/m3.
(e) Calculate the total (or average) molecular weight of the gas mixture (Mt).
(f) Calculate the specific gas constant for this gas mixture (Rt).
(g) Calculate the percentage difference between Rt for this particular gas mixture and that of standard dry air, Rair.
(h) Calculate the total (or average) density for this gas mixture (t).
(i) Assuming standard saturation pressure values for water vapor in air, calculate the relative humidity of this air (RH) as a
percentage.

Download Report