ENCE 433 Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS Spring 2001

Homework Set #4 Out: March 1, 2001 Due: March 6, 2001

1. Write the Mass Balance Equation, Proton Balance Equation (PBE) and the Electroneutrality equation (ENE) for the addition of the following substances to water:

(a) NaCl

(b) NaHCO₃

(c) H₂SO₄

(d) HCl + NaNO₃

(e) NaCl + HCl

2. Sodium hypochlorite (NaOCl), household bleach, is a commonly used disinfectant (pK_a can be found in Table 4.1)

a. Determine the pH of a 1 mM solution

b. Determine the speciation, what are the concentrations of [HOCl] and [OCl^-]

c. Would you need to add acid or base to reach a pH = 7.5

d. What are the concentrations of [HOCl] and [OCl^-] at pH = 7.5

3. Calculate both [H₃O⁺] and [OH^-] in a 0.400 F HCl solution at 25^oC

4. Classify the following salts as acidic, basic, or neutral. Explain your reasoning. (a) (NH₄)₂CO₃, (b) KClO₄, © KHSO₄, (d) BaO, (e) NaHSO₃, and (f) CH₃NH₃NO₃.

5. Calculate the equilibrium pH of a 0.1M nitrous acid, HNO₂, solution at 25^oC

(pK_a = 3.29)