Question

When will a precipitate form? a. When the concentration of the cation is greater than the concentration of the anion. b. When the concentration of the anion is greater than the concentration of the cation. c. When the reaction quotient is greater than the solubility-product constant. d. When the solubility-product constant is greater than the reaction quotient. e. None of these.

Answer 1

c. when the raction quotient is greater than the Ksp

Step-by-step explanation:

• AxBy ↔ xA+ + yB-

∴ Ksp = [ A+ ]∧x * [ B- ]∧y.....solubility product constant

∴ I.P = xA+ * yB-............ionic product

⇒ the relationship between Ksp and I.P, will give us the precipitation conditions.

∴ I.P > Ksp ⇒ precipitation

∴ I.P < Ksp ⇒ no precipitation (disolution)

∴ I.P = Ksp ⇒ equilibrium

⇒ the ionic product is directly related to the reaction quotient Q, where Q = [A+] * [B-] / [AxBy] = PI / [AB], then the higher this product the higher the reaction quotient will be and therefore will be greater than the value of the constant and will have precipitated, the correct answer is the c