ENCE 433 Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS Spring 2001

Homework Set # 5 ALKALINITY

1. Determine the pH and alkalinity for the following solutions. Assume the systems are closed to the atmosphere.

a. 5x10^-4F NaOH

b. 5x10^-5F Na₂CO₃

c. 5x10^-5F KHCO₃

d. 1x10^-3F HCl

2. Water from a deep well is found to have a pH of 6.3 and an alkalinity of 1.00x10^-3 equivalents/l

a) Calculate C_T for this well water prior to equilibration with atmospheric CO₂

_b) Calculate the pH and C_T after equilibration with atmospheric CO₂

_3. Ground water is titrated with acid to find the alkalinity and with base to find the acidity. The results are as follows:

[Alk] = 5.0 x 10^-4 M

[Acy] = 5.0x10^-4 M

Calculate the following: [H⁺], pH, C_T, [H₂CO₃^*] , [HCO₃^-] and [CO₃^-2].

(consider a closed system)

4. Two waters, A: pH = 6,1, [Alk] = 0.5 meq/l; B: pH = 8.5, [Alk] = 2 meq/l, are mixed in equal proportions. What is the pH of the mixture if it is kept closed to the atmosphere? What would happened if pH is kept constant and it equilibrates with atmospheric CO₂?