Question

4. A student purified a 500-mg sample of phthalic acid by recrystallization from water. The published solubility of phthalic acid in 100 mL of water is 0.54 g at 14 oc and 18 g at 99 0C. (a) What is the smallest volume of boiling water the student could use to dissolve 500 mg of phthalic acid?

Answer 1

Answer:

2.77 mL of boiling water is the minimum amount which will dissolve 500 mg of phthalic acid.

Explanation:

We know from the problem that 18 g of phthalic acid are dissolved in 100 mL of water at 99 °C.

Now we devise the following reasoning:

If          18 g of phthalic acid are dissolved in 100 mL of water at 99 °C

Then   0.5 g of phthalic acid are dissolved in X mL of water at 99 °C

X = (0.5 × 100) / 18 = 2.77 mL of water