Chem 217 – Environmental Chemistry

Homework #6

Due Tuesday Apr. 24

From VanLoon and Duffy. (Problem numbers are the same in 3rd and 4th edition unless noted otherwise.)

Chapter 4:

#2 – Write the reaction sequence for reaction of butane (C4H10) with OH to produce an aldehyde (aldehydes have the functional group –CHO). Also write the overall reaction for this process. The net reaction should include the production of 2 molecules of NO2. (See reactions 4.13 – 4.18 in the text). Explain or show how this reaction sequence leads to the production of ozone.

#6 – Think about this problem in terms of a box model, where the amount in the box is the concentration and the loss rate is given by the chemical reaction. Use this to calculate the residence time. You do not need to calculate the half-life.

#7 – Calculate for toluene and hexane only.

Chapter 6:

#3 – Assume sea level pressure (1 atm).

Chapter 7:

#1

#3 (this problem is not in 3rd ed., so I’ve reproduced it here.) A measurement of Air Quality Index given in terms of sulfur dioxide (1 hr) is 109. What is the actual mixing ratio of sulfur dioxide?

Additional Problem:

In May 2015 Ipurchased a VW Golf Diesel Wagon due to the excellent performance and fuel economy (50 mpg at highway speeds). In September 2015 VW acknowledged that they cheated on the emissions test:Everything You Need to Know About the VW Diesel Emissions Scandal. My car is producing 10x more NOx than is allowed by EPA emission limits. It is also producing a lot less CO2 than most other cars. VW is required to provide a fix for the car, but everyone expects this will come with decreased mileage and performance.

Your goal is to determine theenvironmental impacts for a 2015 Turbo Diesel Golf Sportwagon driving in Waterville, specifically whether NOx or CO2 is a greater environmental concern.

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Parameters for the calculation:

  • 10,000 Cars in greater Waterville
  • Assume all cars are 2015 diesels that drive 15,000 miles per year
  • Area of Greater Waterville is 5km x 5km
  • We will use the EPA emission standard of 0.91 g/mile for NOx and assume VW NOx emissions are 10X the legal limit for all cars
  • VW diesel fuel economy is 50 mpg (miles per gallon)
  • Assume a troposphere mixed layer height of 2 km.
  1. Using the information above, calculate the average NOx mixing ratio in Waterville air. Assume a residence time of 1 day for NOx. Show your calculations and assumptions in detail.
  2. Assume a VOC mixing ratio of 0.300 ppm. Using the graph below and the NOx mixing ratio from the previous question, estimate the resulting mixing ratio of ozone.
  3. For each gallon of diesel fuel burned, 10.2 kg of CO2 are emitted. Calculate the CO2 emissions for a single vehicle in g CO2 per mile driven. How does it compare to the EPA emission limit of 245 g/mi (CO2 emissions)? Would a gasoline car with half the fuel efficiency (25 mpg) meet the EPA limit?
  4. Based on your answers, do you think the benefit of higher fuel efficiency (and less CO2 emissions) is worth the tradeoff for higher NOx emissions? Justify your answer.

Note: this problem requires you to perform dimensional analysis, where you determine how to combine the given information based on units. Say you know a car drives 15000 miles/yr, and you want to know how far it drives in one day. It may be helpful to set up an equation, as follows:

We see we can get the answer (x mi) by multiplying 15000 mi/yr by y, the number of years. One day is 1/365 = 0.00274 yr. Substituting this value for y gives:

Hen