Question

The solubility of acid A in water is 200 g/L at 100 C and 5g/L at 10 C. How much mL of water do you need to dissolve 20 g of acid A at 1000 C? How much of this compound would recrystalize out of the solution upon cooling to 10 C? What technique would you use to isolate the product?

Answer 1

The solubility of acid A in water = 200 g/L (at 100 C)S1/T1 =

The solubility of acid A in water = 5 g/L (at 10 C)

The temperature decreases from 100 C to 10 C, the solubility decreases from 200 g/L to 5 g/L

Here, S1 = 200 g/L at T1 = 100 C

And S2 = 5 g/L at T2 = 10 C

i.e. S1*S2 = T1*T2

Now, at 1000 C, the solubility of acid A in water = 100*1000/200 = 500 g/L

i.e. For 20 g of acid A, (20/500)*1000 mL = 40 mL of water should be added to dissolve it.

i.e. The solubility of acid A at 1000 C = 20 g/40 mL and at 10 C = (40/1000)*5 g = 0.2 g/40 mL

Therefore, the compound A that would recrystalize out of the solution upon cooling to 10 C = 20 - 0.2 = 19.8 g

The technique that can be used to isolate the product is filtration.