AP Chemistry : Solubility Rules

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #1 : Solubility Rules

Which of the following will be the precipitate in the following reaction?

 

2KCl + Ca(OH)2 → 2KOH + CaCl2

Possible Answers:

CaCl2

Ca(OH)2

Ca

KOH

No precipitate forms

Correct answer:

No precipitate forms

Explanation:

Though the solubility of calcium hydroxide, Ca(OH)2, is fairly low, it is a reactant and will not form a precipitate. The solid calcium hydroxide will be added to an aqueous solution of potassium chloride, KCl. During the reaction, the calcium hydroxide will transition to potassium hydroxide (KOH) and calcium chloride (CaCl2), both of which are completely soluble. At the end of the reaction, no precipitate will be observed.

Example Question #2 : Solubility Rules

 is dissolved in water. Which of the following salts will result in a precipitate if added to the silver sulfate solution?

Possible Answers:

Correct answer:

Explanation:

This question requires an understanding of solubility guidelines and which ion combinations will result in precipitates. Virtually all ionic compounds containing ammonium, sodium, and nitrate will be soluble in water. Most ionic compounds containing chlorine are soluble, with the exceptions of silver, mercury, and lead cations.

If sodium chloride dissolves in this solution, the silver cations and chlorine anions will combine and result in a white, crystalline silver chloride precipitate.

 

Example Question #3 : Solubility Rules

Which of the following compounds is not soluble in water?

Possible Answers:

Correct answer:

Explanation:

The key to solubility is memorizing the solubility rules. We know that all compounds of alkali metals are soluble. These include potassium, lithium, and sodium, eliminating three of the answers. We also know that all chloride salts are soluble, except those of silver, lead, and mercury. Silver chloride is, thus, not soluble.

All hydroxide compounds are generally insoluble, but alkali metals and ammonium salts will make them soluble. Alkaline earth metals make hydroxides slightly soluble.

Example Question #4 : Solubility Rules

Which of these WILL be soluble in water?

Possible Answers:

FeCl2

CsCl

AgCl

CuCl

Ca2(PO4)3

Correct answer:

CsCl

Explanation:

Solubility Rules: the only soluble ionic compound listed is CsCl; the rest are insoluble due to solubility rules

Example Question #4 : Solubility Rules

Which of the following compounds is insoluble in water?

Possible Answers:

Correct answer:

Explanation:

Unless paired with an alkali metal, carbonate compounds are generally insoluble. Compounds that contain nitrate or an alkali metal will generally be soluble in water, and hydroxides are soluble when paired with heavier alkaline earth metals (such as calcium).

Example Question #5 : Solubility Rules

Which of the following will form a precipitate in solution?

Possible Answers:

None of these will form a precipitate

Correct answer:

None of these will form a precipitate

Explanation:

Standard solubility rules tell us that group I elements and ammonium cations will always result in soluble salts. Lithium, sodium, and potassium are all group I elements, indicating that none of the given answer options will form a precipitate in solution.

Example Question #6 : Solubility Rules

Which of the following ionic compounds is soluble in water?

I. 

II. 

III. 

Possible Answers:

I and II

II and III

I only

I, II, and III

Correct answer:

I and II

Explanation:

Solubility rules determine which ionic compounds are soluble. All nitrates and group I compounds (those containing alkali metals) are soluble. This means that compounds I and II must be soluble; compound I is a nitrate and compound II contains sodium, an alkali metal.

Compound III, calcium fluoride, is not soluble. Most fluoride compounds are soluble, with the exceptions of: .

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