Question

How many milliliters of boiling water are required to dissolve 3.3 g phthalic acid? If the solution were cooled to l4◦C, how many grams of phthalic acid would crystallize out? (The solubility of phthalic acid in water is 0.54 g/100 mL at 14◦C and 18 g/100mL at 99◦C.

Answer 1

In boiling water, the solubility of phalic acid at 99 ^oC is 18 g / 100 mL

This means 18 grams dissolved in 100 mL of water

So, 3.3 g dissolved in = (3.3 g /18 g) * 100 =18.33 mL of water

When is cooled to 14  ^oC the solubility is 0.54 g / 100 mL

This means 0.54 g dissolve in 100 mL of water.

Here we have 18.33 mL of water so now calculate how many grams that can be dissolved in 18 mL at this

temperature,

Number of grams = 0.54 grams * (18.33 mL/100 mL)

=0.099 grams

=0.10 grams

So amount of pthalic acid crystallized is 3.3 g - 0.10 grams = 3.2 grams