The solubilities of ammonium bromide,NH₄Br,in water at 0 °C,20 °C,and 80 °C are as follows:
$The solubilities of ammonium bromide,NH4Br,in water at 0 °C,20 °C,and 80 °C are as follows: Which of the following fractional crystallization schemes would produce the highest percent yield for the recrystallization of ammonium bromide? A) A solution containing 50.5 g NH4Br in 100.0 g H2O at 20 °C is cooled to 0 °C. B) A solution containing 115 g NH4Br in 200 g H2O at 80 °C is cooled to 0 °C. C) A solution containing 120 g NH4Br in 100 g H2O at 80 °C is cooled to 20 °C. D) A solution containing 100 g NH4Br in 100.0 g H2O at 80 °C is cooled to 20 °C. E) A solution containing 95 g NH4Br in 175 g H2O at 80 °C is cooled to 0 °C.$
Which of the following fractional crystallization schemes would produce the highest percent yield for the recrystallization of ammonium bromide?

Question

Quizplus · Accepted Answer

According to the solubility data, the solubility of ammonium bromide increases with temperature. Therefore, the highest percent yield for the recrystallization of ammonium bromide would be achieved by starting with a solution that is saturated at a high temperature and cooling it to a lower temperature to induce crystallization. 
Option C involves starting with a solution containing 120 g of ammonium bromide in 100 g of water at 80°C (i.e., a saturated solution), and cooling it to 20°C. At this lower temperature, the solubility of ammonium bromide decreases to 64 g/100 g of water. Therefore, the excess ammonium bromide will precipitate out of the solution, allowing for high yield recrystallization of the solute.

The Solubilities of Ammonium Bromide,NH4Br,in Water at 0 °C,20 °C,and

The Solubilities of Ammonium Bromide,NH₄Br,in Water at 0 °C,20 °C,and