Waec Model Questions Vol1 2022 Chemistry Question 8

A student carried out a gravimetric determination of the solubility product of calcium fluoride, CaF₂, at 25 °C using the apparatus shown in the diagram. The procedure was: 1. A 250 mL beaker (label A) was filled with distilled water and excess solid CaF₂ was added. The mixture was stirred with a glass rod (label G) until equilibrium was reached at 25 °C (monitored with a thermometer, label F). 2. The saturated solution was filtered through a pre‑weighed filter paper (label C) placed in a filter funnel (label B) attached to a stand. 3. The filtrate was collected in a clean beaker, and the residue on the filter paper was washed with a small amount of cold distilled water. 4. The filter paper with the CaF₂ precipitate was transferred to a pre‑weighed drying crucible (label D) placed on a tripod and dried in an oven. 5. After cooling in a desiccator, the crucible was weighed on an analytical balance (label E). The mass of dried CaF₂ obtained was 0.345 g. 6. In a second trial the student added 0.10 mol of NaF to the saturated solution before filtration and repeated steps 3–5. Using the information above, answer the following questions.