Environmental Chemistry

Homework Assignment 4 (24 points)

1. Water with an alkalinity of 2.00 x 10^-3 equivalents/L has a pH of 7.00. Calculate the [CO₂], [HCO₃^-], [CO₃^2-] and [OH^-]. Use the values for K_a1 and K_a2 given below.
2. 
   Thorough the photosynthethetic activity of algae, the pH of the water in Problem 1 was changed to 10.00. Calculate the new concentrations, at equilibrium for [CO₂], [HCO₃^-], [CO₃^2-] and [OH^-]. Use the values for K_a1 and K_a2 given below.
3. 
   For a solution having 1.00 x 10^-3 equivalents/L total alkalinity (contributions from HCO₃^-, CO₃^2- and OH^-) at [H+] = 4.69 x 10^-11, what is the percentage contribution to alkalinity from CO₃^2-?
4. 
   Calculate the intrinsic solubility for the sparingly soluble mineral gypsum (CaSO₄•2H₂O) in a solution with an ionic strength of 0.001 and a pH of 7.0. Assume that gypsum behaves in water as calcium sulfate (CaSO₄).
5. 
   Calculate the intrinsic solubility for the sparingly soluble mineral gypsum (CaSO₄•2H₂O) in a solution with an ionic strength of 0.001 and a pH of 12.0. Assume that gypsum behaves in water as calcium sulfate (CaSO₄).
6. 
   Calculate the intrinsic solubility for the sparingly soluble mineral gypsum (CaSO₄•2H₂O) in a solution with an ionic strength of 0.100 and a pH of 7.0. Assume that gypsum behaves in water as calcium sulfate (CaSO₄).

   Equations and equilibrium constants for HW-4.

   

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Environmental Chemistry -- ENV 440
Last Updated:  02/02/04