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Assoli18 [71]
3 years ago
13

Solid potassium hydroxide is slowly added to 175 mL of a 0.0621 M cobalt(II) nitrate solution. The concentration of hydroxide io

n required to just initiate precipitation is ...?
Chemistry
1 answer:
Luda [366]3 years ago
8 0

Answer:

[OH⁻] = 3,09x10⁻⁷ M

Explanation:

Selective precipitation is a technique of separating ions in an aqueous solution by using a reagent that precipitates one or more of the ions. In this case, you use OH⁻ from potassium hydroxide to precipitate cobalt thus:

Co(OH)₂ ⇄ Co²⁺ + 2 OH⁻ K_{sp} = 5,92x10⁻¹⁵

The K_{sp} definition is:

K_{sp} = [Co²⁺] [OH⁻]²

Knowing  [Co²⁺] is 0,0621M:

5,92x10⁻¹⁵ = 0,0621M ×  [OH⁻]²

Thus, concentration of hydroxide ion required to just initiate precipitation is: <em>[OH⁻] = 3,09x10⁻⁷ M</em>

<em></em>

I hope it helps!

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