Question

1. Answer the following questions:

a) How does the addition of CaCl₂ affect the molar solubility of Ca(OH)₂?

b) When you add 0.250f of SrF₂ to 1.00L of water, the salt dissolves just a little. Write the balanced equation and write the expresion of Kps.

c) If you find that the balance concentration of Sr²⁺ is 1.03 x 10^-3M, What is the Kps value for SrF₂ ?

d) The Kps value for BaCO₃ is 8.1 x 10^-9 . Write the balanced equation, the Kps expression and calculate the solubility of the salt in pure water in moles per liter.

Answer 1

a) Ca(OH)2 is a strong base, hence, the addition of CaCl2 will not affect the molar solubility of Ca(OH)2 even though it has the common ion (Ca2+) with Ca(OH)2.

b) SrF₂(s) Sr²⁺ + 2F^-(aq)

Ksp of SrF2 = [Sr2+][F-]²

i.e. Ksp = s*(2s)²

i.e. Ksp = 4s³, where 's' i s the solubility of SrF2

c) The balance concentraiton of Sr2+ = [Sr2+] = s = 1.03*10^-3 M

i.e. Ksp of SrF2 = 4*(1.03*10^-3)³

i.e. Ksp of SrF2 = 4.371*10^-9

d) Ksp of BaCO3 = [Ba2+][SO32-]

i.e. Ksp of BaCO3 = s*s

i.e. 8.1*10^-9 = s²

i.e. s = (8.1*10^-9)^1/2

i.e. s = 9*10^-5 M

Therefore, the solubility of the salt in pure water = 9*10^-5 mol/L