ENGS-37                                                                                                           Fall 2008

INTRODUCTION TO ENVIRONMENTAL ENGINEERING

 

HOMEWORK #1

 

Assigned:    Friday 27 September 2008

Due:           10 a.m., Friday 3 October 2008

 

 

1. (5 points)  Environmental engineers can perform remediation of a contaminated site, treatment of an effluent, and prevention of future pollution.  Explore what these different avenues would mean in the case of tri-chloro-ethylene (TCE) at the Cold Regions Research & Engineering Laboratory (CRREL), north of campus in Hanover, New Hampshire.  For background information on this problem, see:

http://yosemite.epa.gov/R1/npl_pad.nsf/31c4fec03a0762d285256bb80076489c/85f637b1452cb01085256b420060669e!OpenDocument

In your answer, you do not need to be very technical.  A sentence or two on the basic approach in each of the three cases will suffice.

 

 

2. (10 points)  Consider the following reaction representing the combustion of propane:

 

                        C3H8   +   O2   →   CO2   +   H2O

 

a. (2 points)  Balance the equation.

b. (2 points)  How many moles of oxygen are required to burn 1 mole of propane?

c. (3 points)  How many grams of oxygen are required to burn 100 g of propane?

d. (3 points)  Under standard conditions (temperature of 25oC, pressure of 1 atmosphere, and oxygen concentration equal to 20% on a volume basis), what volume of air is required to burn 100 g of propane?

 

 

3. (5 points)  (Nazaroff, 2001, page 27, Problem 1.5)  An increase of CO2 in the atmosphere may lead to global climate change.  The mass of the atmosphere is estimated at 5.1 x 1018 kg, while the mole fraction of CO2 in it is currently 380 ppm and is observed to be increasing at a rate of 0.5% per year.  What is the rate of mass accumulation of CO2 in the atmosphere?  Express your answer in metric tons of CO2 per year.

 

 

4. (10 points)  (Nazaroff, 2001, page 27, Problem 1.6)  Combustion of fossil fuels in many different sectors of our human activities is contributing to the increase of CO2 in the atmosphere.  Consequently, improving energy efficiency is considered important for reducing the global atmospheric impact of human activities.  Since much fuel is burned in the US by driving cars and SUVs, let us consider whether improving automotive fuel efficiency might have a significant impact on global CO2 accumulation.

     (a) Assuming that all of the carbon (C) in gasoline is converted to carbon dioxide (CO2) during combustion and using the following data, estimate the CO2 emission rate (in metric tons per year) in the US from private vehicles.

Number of vehicles on the road (N)      = 120 million

Average gas mileage (M)                      = 18 miles per gallon

Average miles traveled (D)                    = 10,000 miles per year per vehicle

Effective fuel composition                      = C8H18

Fuel density (r)                                    = 0.72 g/cm3

     (b) Compare the result of part (a) with that of the preceding problem.  Comment on the potential importance of regulations to improve the fuel efficiency of private vehicles in the US as a means of reducing global CO2 emissions.

 

 

 

 

5. (10 points) (From another textbook)  A typical motorcycle emits 20 g of carbon monoxide (CO) per mile, and the tailpipe emission diffuses in a 10-m2 cross-section behind the cyclist (perpendicular to the direction of travel).  What is the maximum number of motorcycles that can be in a group going one behind another along a street before the CO concentration exceeds to air quality standard of 9.0 ppm?  (Assume complete mixing in the 10-m2 cross-section and that ambient air is at 20oC and 1 atmosphere.)