Question

how many ml of boiling water are required to dissolve 15.0g of phthalic acid? If a solution were cooled too 14 degrees Celsius how many grams of phthalic acid would crystallize out? Determine the percent of recovery

solubility           14°C                100°C

phthalic acid   0.54g/100ml   18g/ml

Answer 1

Solution-

Here let's find the solubility of phthalic acid = 18 g/100 ml at 100 oC or at the boiling water

Now for the 15.0 g we would require = 15 * (100/18)

= 83.33 ml of the boiling water

Now at 14 oC the solution was cooled

The solubility of the phthalic acid = 0.54 g/100 ml at 14 oC

Again in 83.33 ml we have = 83.33 x 0.54/100

= 0.45 g phthalic acid

So finally the mass of phthalic acid crystallized out of solution can be find as
= 15.00 - 0.45
= 14.55 g