Ksp for Mg(OH) 2 = 1.2 X 10 -11 5.6 M C 6 H 5 OH with 1.0 M KC 6 H 5 O 1.0 M C 6

Question

Ksp for Mg(OH)2 = 1.2 X 10-11

5.6 M C6H5OH with 1.0 M KC6H5O

1.0 M C6H5OH with 1.0 M KC6H5O

2.0 M C6H5OH with 1.32 M KC6H5O

1.0 M HCN with 2.0 M NaCN

1.0 MHNO2 with 1.0 M NaNO2

2.0 M HCN with 1.0 M NaCN

If the pH of a solution of magnesium chloride gets too high, magnesium hydroxide (insoluble metal hydroxide) could precipitate from solution. If you prepare a buffer solution, it is possible to prevent the precipitation of Magnesium Hydroxide by controling the pH. Which of the following buffers solutions would not result in the precipitation of Magnesium Hydroxide from a solution that is 0.0173 M in Magnesium chloride . Check all that apply.

Ksp for Mg(OH)2 = 1.2 X 10-11

Weak acid Ka C6H5OH 1.3 X 10-10 HNO2 4.5 X 10-4 HCN 4.0 X 10-10

Explanation / Answer

We need a buffer, that is, conjugate + acid

pH = pKa + log(A-/HA)

we want a low pH

pka = -log(Ka)

pKa Phenol = 9.88

pKa HNO2 = 3.35

pKa HCN = 9.39

NOTE that we want a low pH, this is achieved as follows:

pH = pKa + log(A-/HA)

since log(A-/HA) is pretty low, that is, not more than 2 units, you may assume

pH = pKa

we require low pH to avoid high pH and precipitation so,

chooose:

1.0 MHNO2 with 1.0 M NaNO2

Related Questions

Navigate

• Browse (All)
• Browse K
• Subjects

---

---

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