CHEMISTRY · Multi-part · AP · Chemistry · Acids and Bases · Acids and Bases
Problem
In a marine engineering context, carbon-containing deposits accumulate inside seawater pipes, sometimes leading to mineral scaling. Two common ionic compounds found in these deposits are calcium carbonate, CaCO3, and sodium chloride, NaCl. During routine maintenance, technicians inject a strong acid to lower the pH of the seawater flowing through the pipes from 8.2 to 2.0.
Answer the following questions about the effect of this pH change on the two solids mentioned. Assume temperature remains constant and that no oxidation–reduction reactions occur.
(a) For each anion present in CaCO3 and NaCl, classify the anion as the conjugate base of a strong acid, the conjugate base of a weak acid, or neither. Provide a brief justification in each case.
(b) Describe qualitatively how the solubility of CaCO3 will change when the pH is lowered from 8.2 to 2.0. Include a clear explanation for the predicted direction of change.
(c) Explain why the solubility of NaCl is expected to remain essentially unchanged over the same pH range.
(d) Predict qualitatively how the solubility of silver chloride, AgCl, would be affected if the pH of seawater were instead increased from 8.2 to 11.0. Justify your prediction.