Question

3 od Part A Calculate the solubility (in grams per 1.00 x 10 mL of solution) of magnesium hydroxide in a solution buffered at pH = 12.K.( M Express your answer using two significant figures. OH.) 2.06 x 10 0 AED S - 2.33. 10-4 8/1.00 x 10 mL) Submit Previous Answers Request Answer X Incorrect; Try Again; 3 attempts remaining Part B 2.06 x 10 Calculate the solubility (in grams per 1.00 x 10 mL of solution) of magnesium hydroxide in pure water, K..(Mg(OH).) Express your answer using two significant figures. %AED O ? Pearson

Answer 1

Part A : S₁ = 1.2 x 10^-8g/(1.00 x 10² mL)

Part B : S = 2.2 x 10^-4 g/(1.00 x 10² mL)

Part C : S₁ / S = 5.5 x 10^-5

Explanation

Part A :

pH = 12

pOH = 14 - pH

pOH = 14 - 12

pOH = 2

[OH^-] = 10^-pOH

[OH^-] = 10^-2

[OH^-] = 1.0 x 10^-2 M

Let molar solubility of Mg(OH)₂ = s

[Mg²⁺] = s

[OH^-] = 2s + 1.0 x 10^-2 M

K_sp Mg(OH)₂ = [Mg²⁺][OH^-]²

2.06 x 10^-13 = (s) * (2s + 1.0 x 10^-2 M)²

Solving for s, s = 2.06 x 10^-9 M

volume of solution = 100 mL = 0.100 L

moles Mg(OH)₂ = (concentration Mg(OH)₂) * (volume of solution in Liter)

moles Mg(OH)₂ = (2.06 x 10^-9 M) * (0.100 L)

moles Mg(OH)₂ = 2.06 x 10^-10 mol

mass Mg(OH)₂ = (moles Mg(OH)₂) * (molar mass Mg(OH)₂)

mass Mg(OH)₂ = (2.06 x 10^-10 mol) * (58.32 g/mol)

mass Mg(OH)₂ = 1.2 x 10^-8 g