CHEMISTRY · Multi-part · AP · Chemistry · Acids and Bases · Acids and Bases
Problem
A student titrates 50.0mL of 0.100M acetic acid, CH3COOH (Ka=1.8×10−5), with 0.100M NaOH at 25∘C. The buret reading shows that exactly 50.0mL of the base has been delivered, confirming the equivalence point has been reached.
(a) Identify the major chemical species (other than water) present in the solution at the equivalence point and write a balanced equation for the most important acid–base reaction that still occurs in the beaker.
(b) Explain, without performing numerical calculations, why the pH of the solution at the equivalence point is greater than 7. Your explanation should reference both molecular-level interactions and equilibrium considerations.
(c) Describe two separate experimental modifications—each involving a different variable—that would make the pH at the equivalence point closer to 7. For each modification, explain the chemical reasoning behind the predicted change.