Question

A solution which is 38.0% w/w in k2cro4 has a specific gravity of 1.37. calculate the concentration in terms of molarity of chromate ion.

Answer 1

When in aqueous solution, K2CrO4 dissociates into ions. It dissociates into:

K2CrO4 = 2K+1 + CrO4-1

We do as follows:

Molarity = mol / L = 0.38 g/g solution ( 1.37 g/mL ) ( 1 mol / 194.19 g ) ( 1 mol CrO4-1 / 1 mol K2CrO4 ) ( 1000 mL / 1 L ) =  2.68 M