Question

Compound A has a solubility of 0.2 g/mL in toluene at toluene's boiling point and a solubility of 0.05 g/mL at 0 ºC. How much toluene would be necessary to recrystallize 3.2 g of A. What would be the maximum amount of A that could be recovered if the saturated solution was allowed to cool to 0 ºC. How much A would be recovered, if you accidentally used twice as much toluene as was necessary?

Answer 1

Answer:

1) 16 mL of toluene is necessary to recrystallize 3.2 g of compound A

2) 2.4 g of A is the maximum amount that could be recovered.

3) 1.6 g of compound A  can be recovered if you accidentally use twice as much  toluene as was necessary

Explanation:

1)

The volume of the solvent ( toluene) = $\frac{starting \ amount }{solubility \ at \boiling \ point }$

= $\frac{3.2 \ g}{0.2 \ g/mL}$

= 16 mL

∴  16 mL of toluene is necessary to recrystallize 3.2 g of compound A

2)

The maximum amount    A that could be recovered if the saturated solution was allowed to cool to 0 ºC is determined by the difference of the starting amount and amount left in the solution at 0 ºC

i.e

maximum amount of A = 3.2 - ( 16 mL × 0.05 g/mL)

= 3.2 g - 0.8 g

= 2.4 g

∴  2.4 g of A is the maximum amount that could be recovered.

3)

Amount of A that would be  recovered, if you accidentally used twice as much toluene as was necessary is calculated as follows;

amount of A = 3.2g - (32 mL × 0.05 g/mL)

= 3.2 g - 1.6 g

= 1.6 g

Thus; 1.6 g of compound A  can be recovered if you accidentally use twice as much  toluene as was necessary