A student is performing an acid-base titration to determine the concentration of an ammonia solution, NH3(aq)\text{NH}_3\text{(aq)}NH3(aq). They use a volumetric pipette to transfer a sample of the ammonia solution into a conical flask, and then titrate it with hydrochloric acid, HCl(aq)\text{HCl(aq)}HCl(aq), from a burette.
Upon completing the titration, the student finds that the volume of hydrochloric acid required to reach the end-point is significantly larger than the expected theoretical value. Which of the following is a possible explanation for this result?
The conical flask was rinsed with distilled water prior to the titration.
The volumetric pipette was rinsed only with distilled water prior to being used.
The conical flask was rinsed with hydrochloric acid prior to the titration.
The burette was rinsed only with distilled water prior to being filled with the hydrochloric acid.
77 exam-style questions on AQA A Level Chemistry Acids and bases (A-level only), covering Brønsted–Lowry acid–base equilibria in aqueous solution (A-level only), Definition and determination of pH (A-level only), The ionic product of water, $K_w$ (A-level only), Weak acids and bases $K_a$ for weak acids (A-level only), pH curves, titrations and indicators (A-level only), and Buffer action (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.