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.

Buffers would not result in precipitation are:

*1.0M HNO2 with 1.0M NaNO2 (Ka = 4.5x10⁻⁴; pKa = 3.347)

*5.6M C6H5OH with 1.0M KC6H5O (Ka = 1.3x10⁻¹⁰; pKa = 9.89)

*2.0M HCN with 1.0M NaCN (Ka = 4.0x10⁻¹⁰; pKa = 9.40)

Explanation:

The Ksp of magnesium hydroxide, Mg(OH)₂, is:

Mg(OH)₂(s) ⇄ Mg²⁺(aq) + 2 OH⁻(aq)

Ksp = [Mg²⁺] [OH⁻]² = 1.2x10⁻¹¹

The precipitation will occurs when the product [Mg²⁺] [OH⁻]² > Ksp. If [Mg²⁺] is 0.0173M:

[0.0173M] [OH⁻]² > 1.2x10⁻¹¹

[OH⁻]² > 6.936x10⁻¹⁰

[OH⁻] > 2.63x10⁻⁵M

pOH (-log [OH]) is 4.58, and pH (pH = 14-pOH) is:

pH = 9.42, if pH > 9.42, the precipitation will occurs

For the following options, using H-H equation, pH is:

*1.0M HNO2 with 1.0M NaNO2 (Ka = 4.5x10⁻⁴; pKa = 3.347)

pH = 3.347 + log (1.0M / 1.0M)

pH = 3.347. As pH <  9.42; the buffer solution will not result in precipitation.

*2.0M C6H5OH with 1.32M KC6H5O (Ka = 1.3x10⁻¹⁰; pKa = 9.89)

pH = 9.89 + log (1.32M / 2.0M)

pH = 9.71. As pH >  9.42; the buffer solution will result in precipitation.

*1.0M HCN with 2.0M NaCN (Ka = 4.0x10⁻¹⁰; pKa = 9.40)

pH = 9.40 + log (2.0M / 1.0M)

pH = 9.70. As pH >  9.42; the buffer solution will result in precipitation.

*5.6M C6H5OH with 1.0M KC6H5O (Ka = 1.3x10⁻¹⁰; pKa = 9.89)

pH = 9.89 + log (1.0M / 5.6M)

pH = 9.14. As pH <  9.42; the buffer solution will not result in precipitation.

*2.0M HCN with 1.0M NaCN (Ka = 4.0x10⁻¹⁰; pKa = 9.40)

pH = 9.40 + log (1.0M / 2.0M)

pH = 9.10. As pH <  9.42; the buffer solution will not result in precipitation.

*1.0M C6H5OH with 1.0M KC6H5O (Ka = 1.3x10⁻¹⁰; pKa = 9.89)

pH = 9.89 + log (1.0M / 1.0M)

pH = 9.89. As pH >  9.42; the buffer solution will result in precipitation.

1 is the answer to this problem

here is table 2-2:

country

percent of eligible voters that voted

rank

united states

44.9%

138

canada

60.1%

107

costa rica

84.6%

14

hungary

66.9%

82

japan

57.0%

118

egypt

27.7%

159

south africa

85.5%

10

ans is no, the data set cannot be plotted as a single circle graph