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Key concepts and summary

The equilibrium constant for an equilibrium involving the precipitation or dissolution of a slightly soluble ionic solid is called the solubility product, K sp , of the solid. When we have a heterogeneous equilibrium involving the slightly soluble solid M p X q and its ions M m+ and X n– :

M p X q ( s ) p M m+ ( a q ) + q X n− ( a q )

We write the solubility product expression as:

K sp = [M m+ ] p [X n− ] q

The solubility product of a slightly soluble electrolyte can be calculated from its solubility; conversely, its solubility can be calculated from its K sp , provided the only significant reaction that occurs when the solid dissolves is the formation of its ions.

A slightly soluble electrolyte begins to precipitate when the magnitude of the reaction quotient for the dissolution reaction exceeds the magnitude of the solubility product. Precipitation continues until the reaction quotient equals the solubility product.

A reagent can be added to a solution of ions to allow one ion to selectively precipitate out of solution. The common ion effect can also play a role in precipitation reactions. In the presence of an ion in common with one of the ions in the solution, Le Châtelier’s principle applies and more precipitate comes out of solution so that the molar solubility is reduced.

Key equations

  • M p X q ( s ) p M m+ ( a q ) + q X n− ( a q ) K sp = [ M m+ ] p [ X n− ] q

Chemistry end of chapter exercises

Complete the changes in concentrations for each of the following reactions:

(a) AgI ( s ) Ag + ( a q ) + I ( a q ) x _____

(b) CaCO 3 ( s ) Ca 2+ ( a q ) + CO 3 2− ( a q ) ____ x

(c) Mg ( OH ) 2 ( s ) Mg 2+ ( a q ) + 2 OH ( a q ) x _____

(d) Mg 3 ( PO 4 ) 2 ( s ) 3 Mg 2+ ( a q ) + 2 PO 4 3− ( a q ) x _____

(e) Ca 5 ( PO 4 ) 3 OH ( s ) 5 Ca 2+ ( a q ) + 3 PO 4 3− ( a q ) + OH ( a q ) _____ _____ x

(a) AgI ( s ) Ag + ( a q ) + I ( a q ) x x _
(b) CaCO 3 ( s ) Ca 2+ ( a q ) + CO 3 2− ( a q ) x _ x
(c) Mg ( OH ) 2 ( s ) Mg 2+ ( a q ) + 2 OH ( a q ) x 2 x _
(d) Mg 3 ( PO 4 ) 2 ( s ) 3Mg 2+ ( a q ) + 2PO 4 3− ( a q ) 3 x _ 2 x
(e) Ca 5 ( PO 4 ) 3 OH ( s ) 5Ca 2+ ( a q ) + 3PO 4 3− ( a q ) + OH ( a q ) 5 x _ 3 x _ x

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Complete the changes in concentrations for each of the following reactions:

(a) BaSO 4 ( s ) Ba 2+ ( a q ) + SO 4 2− ( a q ) x _____

(b) Ag 2 SO 4 ( s ) 2 Ag + ( a q ) + SO 4 2− ( a q ) _____ x

(c) Al ( OH ) 3 ( s ) Al 3+ ( a q ) + 3 OH ( a q ) x _____

(d) Pb ( OH ) Cl ( s ) Pb 2+ ( a q ) + OH ( a q ) + Cl ( a q ) _____ x _____

(e) Ca 3 ( AsO 4 ) 2 ( s ) 3 Ca 2+ ( a q ) + 2 AsO 4 3− ( a q ) 3 x _____

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How do the concentrations of Ag + and CrO 4 2− in a saturated solution above 1.0 g of solid Ag 2 CrO 4 change when 100 g of solid Ag 2 CrO 4 is added to the system? Explain.

There is no change. A solid has an activity of 1 whether there is a little or a lot.

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How do the concentrations of Pb 2+ and S 2– change when K 2 S is added to a saturated solution of PbS?

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What additional information do we need to answer the following question: How is the equilibrium of solid silver bromide with a saturated solution of its ions affected when the temperature is raised?

The solubility of silver bromide at the new temperature must be known. Normally the solubility increases and some of the solid silver bromide will dissolve.

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Which of the following slightly soluble compounds has a solubility greater than that calculated from its solubility product because of hydrolysis of the anion present: CoSO 3 , CuI, PbCO 3 , PbCl 2 , Tl 2 S, KClO 4 ?

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Questions & Answers

What is stoichometry
ngwuebo Reply
what is atom
yinka Reply
An indivisible part of an element
ngwuebo
the smallest particle of an element which is indivisible is called an atom
Aloaye
An atom is the smallest indivisible particle of an element that can take part in chemical reaction
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is carbonates soluble
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What is atom? atom can be defined as the smallest particles
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the study of matter
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energy can neither be created or distroyed it can only be transferred or converted from one form to another
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Graham's law of Diffusion
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Scientific notation for 150.9433962
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aromaticity is a conjugated pi system specific to organic rings like benzene, which have an odd number of electron pairs within the system that allows for exceptional molecular stability
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sodium hydroxide (NaOH)
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is simply means a condensed water vapour
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a hydrocarbon contains 7.7 percent by mass of hydrogen and 92.3 percent by mass of carbon
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they are three 3
Adazion
TYPES OF COVALENT BOND-POLAR BOND-NON POLAR BOND-DOUBLE BOND-TRIPPLE BOND. There are three types of covalent bond depending upon the number of shared electron pairs. A covalent bond formed by the mutual sharing of one electron pair between two atoms is called a "Single Covalent bond.
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Practice Key Terms 4

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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