Question

Suppose each of the following substances is added to a saturated solution of iron(III) phosphate. Which will increase the solubility of iron(III) phosphate, and which will decrease the solubility of iron(III) phosphate, and why?

a. Fe(NO3)3

b. NaOH

c. K3PO4

d. HCl

Answer 1

FePO4 <-----> Fe⁺³ + PO4^3-

a) If we add Fe(NO3)3 to the saturated iron(III) phosphate, Fe+3 ion concentration increases due to common ion effect and reaction moves towards backward and solubility of iron(III) phosphate decreases.

b) If we add NaOH to the saturated iron(III) phosphate, no common ions.No change in the solubility of iron(III) phosphate.

c) If we add K3PO4 to the saturated iron(III) phosphate, phosphate ion concentration increases due to common ion effect and reaction moves towards backward and solubility of iron(III) phosphate decreases.

d) If we add HCl to the saturated iron(III) phosphate, no common ions.No change in the solubility of iron(III) phosphate.