Homework #3

1. Chemical Dosing

a. How many mg/L of chlorine (hypochlorous acid) are required to oxidize 0.8 mg/L ferrous iron to ferric iron? Express your answer in mg/L as Cl₂.

b. How many mg/L of potassium permanganate[1] are required to oxidize 2 mg/L of cyanide to nitrate and carbon dioxide?

2. List all possible species and write the necessary equations (equilibrium, mass balance, and electroneutrality) to solve the following chemical systems.

a. 10^-5 M sodium acetate and 10^-6 M acetic acid

b. 10^-5 M sodium dihydrogen phosphate and 10^-6 M disodium hydrogen phosphate

c. 10^-4 M hydrochloric acid

d. 10^-4 M acetic acid

3. Determine the Percent composition (% acetate, % acetic acid) of a solution of Acetic Acid at the following pHs

a. pH 3.0

b. pH 4.5

c. pH 5.5

Assigned: 1 Oct 10

Your Name: ____________________________________

Due: 8 Oct 10

Your Name: ____________________________________

Answer Page

Fill in the boxes with the correct answer.

You will only get credit for a problem if you (1) fill in the box with the correct answer, (2) your answer is legible, and (3) you include attach page(s) with calculations backing up your answer, when requested for the problem.

Problem #

1		mg/L as Cl₂
1		mg/L as KMnO₄

2a	Species
	Equilibria
	Mass balances
	Electro-neutrality

2b	Species
	Equilibria
	Mass balances
	Electro-neutrality

2c	Species
	Equilibria
	Mass balances
	Electro-neutrality

2d	Species
	Equilibria
	Mass balances
	Electro-neutrality

3	a	% acetic acid	% acetate
	b	% acetic acid	% acetate
	c	% acetic acid	% acetate

[1] Permanganate is a strong oxidant that is widely used in water treatment and for COD tests and some toxic waste treatment systems. Manganese is the oxidized species that does the “work” and its final reduced form after treatment is as manganese dioxide.