The hydroxide ion has the formula OH. The solubility-product constants for three

Question

The hydroxide ion has the formula OH. The solubility-product constants for three generic hydroxides are given here.

Use these values to answer the following questions.

Part A

The removal of an ion is sometimes considered to be complete when its concentration drops to 1.00×106  M. What concentration of hydroxide would cause Y2+ to "completely" precipitate from a solution?

Express the molar concentration numerically.

Part B

At a pH of 10.5, arrange the solutions containing the following generic hydroxides in order of decreasing concentration of the cation remaining in the solution (i.e., in order of increasing completeness of precipitation).

Y(OH)2, Z(OH)3, XOH

Highest concentration - Lowest concentration

Explanation / Answer

a) Since - Ksp of Y(OH)2 = 2.20*10-10

Ksp = [Y2+][OH-]2

2.20*10-10 = (1.00*10-6)[OH-]2

[OH-] = 0.0148 M

b) At pH = 10.5, pOH = 3.5, hence [OH-] = 10-3.5 M = 3.162*10-4 M

For Y(OH)2,   [Y2+] = 2.20*10-10 / (3.162*10-4 )2 = 0.0022 M

For Z(OH)3 , [Z3+] = 7.20*10-15 / (3.162*10-4 )3 = 2.27*10-4 M

For XOH , [X+] = 1.8*10-8 / (3.162*10-4) = 0.180 M

Therefore decreasing order of metal ion concentration = XOH > Y(OH)2, > Z(OH)3

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.