The solubility of a compound in two solvents is shown in the table below. Based
ID: 569330 • Letter: T
Question
The solubility of a compound in two solvents is shown in the table below. Based on this information, which is the better solvent choice for recrystallization? 5. Solvent Solvent A Solvent B 7.2 g per 100mL 59 g per 100mL solubility while in ice bath 0.22 g per100mL 30 g per 100mL a. Solvent A is better because it has the least solubilty at low temperature b. Solvent B is better because the difference in solubility is the greatest between hot and cold. c. Solvent B is better because the compound is more soluble at hot temperatures. d. Neither solvent A nor B is better, they are both good choices for recrystallization.Explanation / Answer
Ans. # % recrystallization in solvent A =
(solubility at BP – Solubility in ice bath) / Solubility at BP
= [(7.2 g / 100 mL) – (0.22 g/ 100 mL)] / (7.2 g / 100 mL)
= 96.94 %
That’s, in solvent A, 96.94 % of solutes would be recrystallized and the rest (3.06 %) would be lost in the solvent.
# % recrystallization in solvent B =
(solubility at BP – Solubility in ice bath) / Solubility at BP
= [(59 g / 100 mL) – (30 g/ 100 mL)] / (59 g / 100 mL)
= 49.15 %
That’s, in solvent B, only 49.15 % of solutes would be recrystallized and the rest (50.85 %) would be lost in the solvent.
# Therefore, A is a better solvent for recrystallization (96.94 % compared to 49.15 % in solvent B) because it cause much lower loss of solutes (3.06 % compared to 50.85 % in solvent B) in the solvent.
In summary, a solvent that is least solubility for the solute at lower temperature is preferred as better solvent for recrystallization it causes relatively lesser loss of solutes in solvent during recrystallization.
# So, correct option is- a. Solvent A is better because ----