Question

You need to purify 2.0 grams of an impure sample of Acetanilide. The sample is contaminated with aniline. After the purification is complete you isolate 0.8 grams of acetanilide and record a melting point range of 108-110 °C. Complete the following calculations and show your work.
a. Calculate the minimum amount of distilled water you would use to complete the recrystallization.
b. How much acetanilide will still be dissolved in solution even after the sample is cooled to 0 °C?
c. Calculate the % recovery and the % error for the melting point.
d. Why is the percent recovery less than 100%? Describe multiple sources for loss of sample.

Answer 1

Answer:

Following are the answer to this question:

Explanation:

In the given question an attachment file is missing, that is attached. please find the attached file, and the following are the description of the given points:

a. At 100 degrees in 100 mL 5 g is dissolved.  

For, it required:

$\to 2g = 100 \times \frac{2}{5}$

         $= 40 \ \ ml \ of \ water.$  

b. At 0 degrees 100 mL dissolve in 0.3 g.  

So, the dissolve:

$\to 40 \ ml= 0.3\times \frac{40}{100}$

               $= 0.12g.$

After refrigeration 0.12 g will still be dissolved.  

c. After dissolving and freezing, precipitation can occur which would still be impure if the cooling is instantaneous. The added solvent was also too hard to recrystallize. The solvent was placed below its place of reservation.  

d. Recovery percentage:

$\to \frac{0.8}{2}\times100$

$\to 40 \ \%$

The melting point of acetanilide:

$\to 114.3^{\circ}.$

Found=109(medium)  

Melting point error percentages:

$= \frac{114.3-109}{114.3}\\\\=4.63 \ \%$