Question

The K_sp for M₂X₂, a slightly soluble ionic compound is 4.5 x 10^-29. The electron configuration of M₂⁺² is prepared Xe6s¹5d¹⁰4f¹⁴. The X^- anion has 54 electrons. What is the molar solubility of M₂X₂ in a solution of NaX prepared by dissolving 1.98 grams of NaX in water and diluting to 150 ml?

Answer 1

X - has 54 electrons means . X is neutral it has 53 electrons . so it is iodine

Iodine molar mass = 127 g/ mol

NaX = NaI = molar mass = 150 g/mol

NaI molarity = (1.98 / 150 ) x 1000 / 150

                      = 0.088 M

[X-] = 0.088 M

M2X2 -----------------------> M2+2 + 2 X-

                                            S            2S ---------------> in absence common ion

                                           S             2S+0.088 ---------------> in presence common ion

Ksp = [M2+2][X-]^2

Ksp = (S ) (2S+0.088 )^2

compared to 0.088 , 2S can be ignored

Ksp = (S ) (0.088 )^2

4.5 x 10^-29 = (S ) (0.088 )^2

S = 5.81 x 10^-27 M

molar solubilty = 5.81 x 10^-27 M