Neco Model Questions Vol1 2017 Chemistry Question 8

A student carries out a solubility experiment to determine the solubility of calcium fluoride (CaF₂) in water at two different temperatures using the apparatus shown. The apparatus consists of a 250 mL beaker placed on a thermostatically controlled water‑bath, a calibrated thermometer, a magnetic stirrer with a stir bar, a filter funnel fitted with filter paper, and a digital analytical balance. The student adds excess solid CaF₂ to 250 mL of distilled water, heats the water‑bath to the required temperature, stirs until equilibrium is reached, then quickly filters the saturated solution and weighs the amount of solid that remained undissolved. The data obtained are: - At 25 °C, 0.50 g of CaF₂ remained undissolved. - At 40 °C, 0.85 g of CaF₂ remained undissolved. Using this information, answer the following questions: