1. Environmentalengineeringbasics(4points;1each)

Provide a brief, accurate response to each of the following problems or questions. Your responses should demonstrate your clear understanding of key concepts.

(a) Consider a parcel of air that has a fixed temperature, T, and pressure, P, and composition.

The temperature increases. Does the air density increase, decrease, or stay the same?

Explain.

(b) Tetrachloroethylene (C2Cl4, MW = 166 g/mol), also known as PE, is an organic solvent used

for dry cleaning clothes. It is regulated in the US as a drinking water contaminant. The drinking water standard is 0.005 mg/L. What is the corresponding level of PCE in water, expressed in units of ppb?

(c) What is transferred from one species to another in a redox reaction?

(d) A cloud droplet in the unpolluted atmosphere has pH = 5.6. Why isnt the pH equal to 7?

2. NAPLofnaphthalene(4points)

A sealed vessel contains liquid water and air. A quantity of M = 3 millimoles of naphthalene (C10H8, MW = 128 g/mol) is injected into container. Given the data below, determine the equilibrium quantity of NAPL naphthalene in this vessel. Express your answers in millimoles.

[Hint: The final solution does indeed

have a NAPL.]

Henrys law constant for naphthalene (saturation) vapor pressure of naphthalene water solubility of naphthalene temperature

volume of air in the container volume of liquid water in the container

Data:

KH = 2.3 M atm-1 Psat = 10.6 Pa Csat = 31 mg/L T = 298 K

Va = 45 L = 0.045 m3 Vw = 5 L

3. Environmentalredox:Industrialboilers(4points)

In industrial boilers, dissolved oxygen can be a potent corrosive agent, causing iron to rust. Write a stoichiometrically balanced reaction in which solid iron metal (Fe(s)) is converted to iron rust (Fe3+) in water with dissolved oxygen (O2) as the oxidizer.

4. Combustionofasyntheticfuel(4points)

Dimethyl ether (DME, CH3OCH3, MW = 46 g/mol) is a synthetic liquid fuel that can be produced from natural gas or coal and used in motor vehicles. What is the air-to-fuel mass ratio for complete, stoichiometric combustion of DME in air? In other words, how many grams of air are required for complete, stoichiometric combustion of one gram of DME? [Hint: As usual, represent air as a two-component mixture, O2 + 3.78 N2, MW = 29 g/mol.]

5. Neutralizingastrongacidwithastrongbase(4points)

Aqueous wastes with a pH 12.5 or 2 are classified as hazardous because they are corrosive. They must be treated before disposal. Consider pure water to which is added a strong acid such that the initial solution has pH = 2.0. What dose of the strong base, NaOH (MW = 40.0 g/mol), is required to neutralize the acid so that the final solution has pH = 7.0? Express your answer in g/L.