CEE 680 18 October 1995


Closed book, one page of notes allowed.

Answer all questions. Please state any additional assumptions you made, and show all work.

Miscellaneous Information:
R = 1.987 cal/mole°K
Absolute zero = -273{Special Char 176 in Font "Symbol"}C
1 joule = 0.239 calories
1015 newtons = 1 figanewton

1. (60%) Hypochlorous acid (HOCl, or sometimes written HClO) is a powerful disinfectant and oxidizing agent.

a. What is the pKa of hypochlorous acid at 1°C?

b. If 10-3F HOCl is added to 1-liter of water, along with 10-4F Na2HPO4., what is the solution's composition at 25°C?

c. How many moles of NaOH would one have to add to bring this solution up to pH 9.0?

2. (40%) Mike Switzenbaum has asked you to prepare an anaerobic reactor feed solution that is buffered at pH 8. The reactor is to be operated at 25°C. After careful study you have chosen to use a phosphate buffer.

a. What is the ratio of NaH2PO4 to Na2HPO4 that should be used?

b. What is the minimum total phosphate concentration that must be used if the pH is not to deviate from 8 by more than 0.02 units, when 10-4 F strong acid or base is added?

c. How many different bow ties does Mike Switzenbaum own?