An analytical chemist is performing a titration to determine the exact concentration of citric acid in a sample of lime juice. They use a volumetric pipette to transfer 20.0 cm3 of the lime juice into a conical flask and fill a burette with a standard 0.100 mol dm-3 potassium hydroxide solution.
Explain two practical steps (excluding the initial rinsing and calibration of the apparatus) that the chemist should perform during the titration to ensure that an accurate titre volume of potassium hydroxide is obtained. For each step, explain why it improves the accuracy of the result.
157 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.