Problems:

3-12 Bisulfite ion can act as a weak acid and ionize further:

HSO₃^- ↔ H⁺ + SO₃^2-

Given that K_a for HSO₃^- is 1.2 x 10^-7, calculate the concentration of SO₃^2- that is present in the raindrops of pH 4.4 discussed above. [Hint: The concentrations of bisulfite and hydrogen ion will be very close to their values established previously.]

K_a = 1.2 x 10^-7 = [H⁺][SO₃^2-]/[HSO₃^-] = (4 x 10^-5)[SO₃^2-]/(4 x 10^-5) (using values given in text for [H⁺] and [HSO₃^-]). [SO₃^2-] = 1.2 x 10^-7 M

3-17

What would be the correct PM symbol for an index that included only ultrafine particles?

PM_0.1.

What would be the PM symbol for the TSP index? just PM or PM_∞.

Numerically, would the value for the ultrafine component of a given air mass be larger or smaller than its TSP? PM_0.1 would be less than PM_∞.

Review Questions:

3-13 What are the main anthropogenic sources of sulfur dioxide? Describe the strategies by which these emissions can be reduced. What is the Claus reaction?

The main sources are coal burning (where sulfur typically is at percent quantity), certain metal smelters (where sulfur is used to reduce metal oxides), and petroleum or natural gas operations.

3-14 What species are included in the air pollution index called total reduced sulfur?

The species are H₂S, CH₃SH, (CH₃)₂S, and CH₃SSCH₃.

3-16 What two species, other than O₂, are active oxidizing agents of sulfur dioxide in atmospheric particles?

O₃ and H₂O₂.

3-18 Define the term aerosol, and differentiate between coarse and fine particulates. What are the usual origins of these two types of atmospheric particles?

Aerosol is a suspension of liquid or solid particles in a gas. Coarse particulates are larger than (diameter greater than) 2.5 mm while fine particles are smaller than that limit. Most coarse particles are formed as primary aerosol particles from primary mechanical processes (like wind over soil). Fine particles have both primary combustion sources and secondary sources from processes such as photochemical oxidation of hydrocarbons and cloud processing of sulfur dioxide.

3-20 Write a balance equation illustrating the reactions that occur between one molecule of ammonia and (a) one molecule of nitric acid and (b) one molecule of sulfuric acid.

a) NH₃(g) + HNO₃(g) ↔ NH₄NO(s)

b) NH₃(g) + H₂SO₄(g) ↔ NH₄HSO₄(s)