mid term exam w2012

8/2/2019 Mid Term Exam W2012

1/6


2/6

Environmental Chemistry CH601 February 21, 2012Dr. Jean-Paul Simjouw

Mid-term Take Home Examination

Due on February 28, 2012

This exam consists of 16 questions on 3 pages for a total of 100 points. Writeyour answers along with the questions in a word document. Post your responsein Blackboard using the provided link.

Some of the questions are meant to dig a little deeper than the material presentedso far. Try to be as complete and concise as possible with your answers to thequestions. Do not panic if you are unable to get the whole answer. Give me as

much information that is relevant to answering the question as possible.Cite and reference all outside sources you might have used.Work alone.

1. What are the five major classes of material making up the composition ofatmospheric aerosol particles?

An aerosol is defined in its simplest form as solid or liquid particles suspendedin a gas, and it includes a wide range of phenomena such as dust, fume, smoke,mist, fog, haze, and smog.

2. The size distribution of particles emitted from coal-fired power plants is bimodal(is it?). What are some of the properties of the smaller fraction in terms of potentialenvironmental implications?

Using Stokes Lawv = gd 2(pl-p2)

18'1

determine the settling velocity of a particle that has a radius of 2.0 IJm and a densityof 1.5 g mL- 1 . How many days will it take for this particle to fall from a 150 m smoke

stack? How far would this particle travel if the power plant was located inConnecticut?

3. Although NO x is necessary for smog formation, there are circumstances where itis plausible that moderate reductions of NO x levels might actually increase the rateof smog formation. Suggest a reason why this might be so.


3/6


4/6

4. Speculate on how smog reactions would (not) change if the ozone layer would nolonger be present.

5. What important photochemical property do carbonyl compounds share with N0 2?

6. State two factors that make the stratosphere particularly important in terms ofacting as a region where atmospheric trace contaminants are converted to other,chemically less reactive, forms.

7. Which of the following statements is true?a) RO reacts with NO to form alkyl nitratesb) RO is a free radicalc) RO is not a very reactive speciesd) RO is readily formed by the action of stable hydrocarbons and ground state

N0 2e) RO is not thought to be an intermediate in the smog-forming process.

8. The hydroxyl radical is a catalyst for ozone destruction. Show why it is considereda catalyst.

9. Which of the following silicates is more likely to dissolve by weathering: feldsparor olivine? Why?

10. For soils that contain no carbonate, iron, or aluminum, how can neutralization ofacid take place? Write a reaction.

11. Under what conditions do the reactions,

and

occur in soil? Name two detrimental effects that can result from these reactions.


5/6


6/6

12. Because of favorable kinetics, Fe(OH)3(s) is usually regarded as the principalFe(lll) redox species in flooded soils within a few months after inundation. Given theinformation in Table 6.2 of the extra handout and the reaction:

10gK = -7.5

Construct a pE-pH diagram for the species Fe2+, FeC03(s) and Fe(OH)3(s).Take [Fe 2+]= 10- 7 and PC0 2 = 10- 2 atm

13.What are four important effects of organic matter in soil?

14. Calculate the cation exchange capacity of 1 g of soil that releases the followingconcentration of ions in the ammonium acetate test.

Ca 2+= 30.8 Ilg/mlMg2+ = 8.4 Ilg/mlK+= 2.2 Ilg/mlNa' = 6.4 Ilg/ml

15.The soil mineral orthoclase can weather to kaolinite and gibbsite under humidtropical conditions. Write a balanced chemical reaction for this reaction.

16.ln respect to its soil solution chemistry, fulvic acid can be represented by theformula HL, where L- represents 1 mol of dissolved fulvic acid charge, regardless ofthe nature of the organic ligands involved.Use this convention to write a balanced chemical reaction for the congruentdissolution of kaolinite, with the complex, AI(OHhL, as one of the products.

mid term exam w2012

Documents