A student is preparing to perform an acid-base titration where nitric acid, HNO3(aq)\text{HNO}_3\text{(aq)}HNO3(aq), is added from a burette to neutralise potassium hydroxide solution, KOH(aq)\text{KOH(aq)}KOH(aq), in a conical flask. The volume of potassium hydroxide is measured using a volumetric pipette. Upon completing the titration, the student notes that the volume of nitric acid required to reach the end-point is larger than the expected theoretical value. Which of the following is a possible reason for this?
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 to measure the KOH(aq)\text{KOH(aq)}KOH(aq).
The burette was rinsed only with distilled water prior to being filled with the HNO3(aq)\text{HNO}_3\text{(aq)}HNO3(aq).
The conical flask was rinsed with the HNO3(aq)\text{HNO}_3\text{(aq)}HNO3(aq) prior to the titration.
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.