THE UNIVERSITY OF WESTERN ONTARIO
FACULTY OF ENGINEERING
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
CEE 217: INTRODUCTION TO ENVIRONMENTAL ENGINEERING
ASSIGNMENT # 4
(Due October 13, 2006)
Note: 1. Two marks are reserved for properly arranged submission of assignments
2. Please type your name and student number clearly on front cover page
1. The rate at which sunlight reaches the outer edge of the atmosphere of earth is
1370 W/m2 (the solar constant for earth). The earth’s orbit has an average radius
of 150 x 106 km. Since solar radiation decreases as the square of the distance from
the sun, estimate the solar constants for
(a) Mars, whose orbit has a radius of 228 x 106 km.
(b) Venus, whose orbit has a radius of 108 x 106 km.
Answer: (a) 593 W/m2, (b) 2643 W/m2
2. Objects not only radiate energy, but they absorb radiant energy as well. The net
black body radiation for an object at temperature T1 in an environment with
temperature T2 is given by
Enet = A [(T1)4 - (T2)4]
Suppose an unclothed human body has a surface area of 1.35 m2 , an average skin
temperature of 32 C, and is in a room with surface at 15C.Treating this person
as a blackbody (a very good approximation),find the net heat loss by radiation
(watts).
Answer: 136 W
3. Mars radiates energy with a peak wavelength of 13.2 m.
(a) Treating it as a blackbody, what would its temperature be?
(b) What would be the frequency and energy content of a photon at that
wavelength?
Answer: (a) 219 K,
(b) 1.5 x 10-20 J/photon
4. Consider the following reaction representing the combustion of propane:
C3H8 + O2  CO2 + H2O
(a)
(b)
Balance the equation.
How many moles of oxygen are required to burn 1 mol of
propane?
(c)
How many grams of oxygen are required to burn 100g of propane?
(d)
At standard temperature and pressure, what volume of oxygen
would be required to burn 100 g of propane? If air is 21 percent
oxygen, what volume of air at STP would be required?
(e)
At STP what volume of CO2 would be produced when 100 g of
propane are burned?
Answer: (c) 363.6 g O2, (d) 1.21 m3 air, and (e) 0.153 m3 CO2
5. An unknown substance is empirically determined to be 40.00 percent carbon by
weight, 6.67 percent hydrogen, and 53.33 percent oxygen. Its molecular weight is
roughly 55 g/mol. Determine the molecular formula and its correct molecular
weight.
6. The earth’s ozone layer is under attack in part by chlorine released when ultraviolet
radiation breaks apart certain fluorocarbons.Consider three fluorocarbons known as
CFC-11 (CCl3F),CFC-12 (CCl2F2), and HCFC-22 (CHF2Cl).
(a) calculate the percentage by weight of chlorine in each of these
fluorocarbons.
(b) If each kilogram of CFC-11 could be replaced by 1 kg of HCFC-22, by
what percentage would the mass of chlorine emission be reduced?
Answer: (a) CFC-11 (CCl3F): Cl = 77.4%
CFC-12 (CCl2F2): Cl = 58.6%
HCFC-22 (CHF2Cl): Cl = 41.0%
(b) 47%
7. Suppose total world energy consumption of fossil fuels, equal to 3 X 1017 kJ/yr,
were to be obtained entirely by combustion of petroleum with the approximate
chemical formula C2H3. Combustion of petroleum releases about 43 X 103 kJ/kg.
Estimate the emissions of CO2 per year.
Answer: 2.27 x 1013 kg CO2 per year
THE UNIVERSITY OF WESTERN ONTARIO
FACULTY OF ENGINEERING
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
CEE 217: INTRODUCTION TO ENVIRONMENTAL ENGINEERING
ASSIGNMENT No. # 4
(Due October 13, 2006)
Please type your name and student number before printing
Name:
Student No.:
Total Marks:
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