Part 1 of 2. For the HSC Chemistry syllabus dot-point: “Perform a first-hand investigation and solve problems using titrations including the preparation of standard solutions, and use available evidence to quantitatively and qualitatively describe the reaction between selected acids and bases”. This experiment is important because it is one of the most commonly chosen experiments for Prac Exams. Prac Exams could come any time throughout year 12 – but most of the time they occur as part of your trial HSC exams, and usually worth around 20% of total internal assessment. Therefore it is important to pay close attention to proper titration procedure and understand the underlying processes of neutralization reactions.
For this titration, our unknown was a solution of NaOH (the analyte) and our standard solution was oxalic acid (crystals in dihydrate form) – the titrant. Glassware was rinsed properly with either deionised water or with the solution it was to contain (conical flask, volumetric flask – water / pipette, burette – solution). A total of 1 ‘rough titre’ and 3 accurate titres were done. The average of the 3 accurate titres were recorded and used to finally calculate the concentration of the unknown NaOH. Our indicator was phenolphthalein due to its slightly basic endpoint (the titration was between a strong base and a weak acid, therefore the equivalence point would be slightly basic). Tip: If required to make your own standard solution, make sure you design your standard solution so that it was enough moles for you to do 3 titres.