(a) If the total concentration of acetic acid ([CH3COOH] + [CH3COO- ]) in a river is 3 x 10-3 moles per liter and the pH of the river water is 4.8, what is the concentration of negative charge due to the acetate ions? [The pKa value of acetic acid is 4.8.]
The answer is 1.5*10^-3 moles (-)/L
(b) Propionic acid is CH3CH2COOH, and its pKa is 4.9. If propionic acid occurs in a river and the pH of the river water is 8, what is the ratio of (CH3CH2COO - ) to (CH3CH2COOH) in the water?
(c) Assume that the total concentration of propionic acid in a river is 1 x 10-3 moles per liter and the total concentration of acetic acid is 3 x 10-3 moles per liter. If these two acids were the only organic compounds in the river, what would be the concentration of dissolved organic C in the water (in mg L-1 )?