Question

the solubility of a compound is 7.2 g / 100 ml in water at 95 °c and 0.22 g / 100 ml at 2 °c. if you take 7.2g of compound and dissolve it in 100 ml of boiling water and then cool it down to 2 °c and filter it (as above), you would recover ____ % (round your answer to 2 significant figures)

Explanation:

Step1: Determine the amount of compound remaining in solution at 2°C

The solubility at 2°C is 0.22 g/100 mL. When 100 mL of solution is cooled to 2°C, the amount of compound that remains dissolved is 0.22 g.

Step2: Calculate the amount of compound recovered

The initial amount of compound is 7.2 g. The amount recovered $m = 7.2 - 0.22=6.98$ g.

Step3: Calculate the percentage recovery

The percentage recovery $P=\frac{m}{7.2}\times 100\%=\frac{6.98}{7.2}\times 100\% \approx 97\%$

Answer:

97%