ENCE 433 Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS Spring 2001

Homework Set # 5 Out: March 15 Due: March 27

1. A 24.00 mL portion of an aqueous solution of HBr of unknown concentration is titrated with 0.1500 F NaOH. The equivalence point is reached when 32.80 mL of base has been added. Calculate the concentration of the hydrobromic acid.

2. If 100 mL of water are added to 100 mL of a buffer that is 0.200 F NH₄NO₃ and 0.200 F NH₃, what effect does this dilution have on the pH of the buffer?

3. You have an industrial wastewater composed entirely of 0.01 F Sodium Bisulfide (NaHS) and 0.000316 F Propionic Acid (C2H5COOH). What is the equilibrium composition of this mixture?

Approach

· construct Log C vs pH Diagram

· pKa's are 7.02 and 13.9 for sulfide system and 4.87 for propionic acid (from table)

· write PBE to get intersection

· read off concentrations

4. What would the pH be if you added 0.005 F HCl to the wastewater in previous question?

Approach

· use previously constructed Log C vs pH Diagram

· write ENE to get intersection

· read off concentrations