VERY HARD Precipitation Titration Question | Year 12 HSC Chemistry Module 8 скачать в хорошем качестве

VERY HARD Precipitation Titration Question | Year 12 HSC Chemistry Module 8

Question 33 from the 2023 James Ruse Agricultural High School HSC Chemistry Trial Paper An investigation was carried out using a series of precipitation reactions to determine the concentration of magnesium, silver, and copper ions presents in a sample solution. A 25.0 mL aliquot of the sample solution was pipetted into a conical flask. That solution was reacted with hydrochloric acid solution until no more precipitate was formed. The precipitate was extracted using gravity filtration, allowed to dry overnight and was found to have a mass of 1.36 g. The filtrate was collected into a separate conical flask. That solution was treated with a dilute ammonia solution to neutralise the remaining hydrochloric acid. Sodium hydroxide solution was added to the resultant solution until no more precipitate was formed. A mixture of blue and white precipitates was obtained in the conical flask. The precipitates were filtered, dried in an oven, and recorded to have a mass of 2.40 g. In a separate experiment, a fresh 20.0 mL aliquot of the sample solution was pipetted into a conical flask and titrated with a 0.427 mol L–1 solution of sodium carbonate. During this precipitation titration a series of coloured precipitates formed, starting with a pale, yellow silver precipitate, then a blue copper precipitate, followed by a white magnesium precipitate. The titre volume was recorded once a white precipitate had begun to form in the conical flask. The results of the precipitation titration are given in the table: Titration Volume of Na2CO3 (mL) 1 41.10 2 39.75 3 39.85 4 39.80 Calculate the concentrations of magnesium, silver, and copper ions in the original sample solution. Include a relevant chemical equation for each precipitation reaction.