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LEARNING OUTCOMES

C12-1-02: Perform a laboratory activity to develop a set of solubility rules

C12-1-03: Use a table of solubility rules to predict the formation of a precipitate

SOLUBILITY RULES

• Solubility rules allow people to predict if a precipitate will form, and if one does---what it is!

• Solubility rules rely on standard known solubilities for ions at STP (standard temperature and pressure: 0C and 101.3 kPa)

• In order to use the solubility rules to your advantage when predicting the product of the combination of two ionic solutions you must be able to write a net ionic equation

WRITING NET IONIC EQUATIONS

Step 1: Predict the products of the reaction and ensure that the equation is balanced

Think double-displacement reaction

Example: Reaction between BaCl2 and Na2SO4

BaCl2 + Na2SO4 BaSO4 + NaCl

WRITING NET IONIC EQUATIONS

Step 2: Balance the equation

BaCl2 + Na2SO4 BaSO4 + 2NaCl

WRITING NET IONIC EQUATIONS

Step 3: Use a table of solubility rules to identify which ionic substances will precipitate from aqueous solutions

Precipitate is a solid give it an ‘s’ subscript and the rest an ‘aq’ subscript

BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)

This is known as a balanced molecular equation

WRITING NET IONIC EQUATIONS

Step 4: Separate the aqueous solutions into their ions

Ba2+ (aq) + 2Cl-

(aq) + 2Na+(aq) + SO42-

(aq) BaSO4(s) + 2Na+

(aq) + 2Cl-(aq)

This is known as an ionic equation

WRITING NET IONIC EQUATIONS

Step 5: Cancel out spectator ions

Ba2+ (aq) + 2Cl-

(aq) + 2Na+(aq) + SO42-

(aq) BaSO4(s) + 2Na+

(aq) + 2Cl-(aq)

Ba2+ (aq) + SO42-

(aq) BaSO4(s)

This is a net ionic equation

SOLUBILITY RULES

A set of rules to help you predict if and what precipitate will form when combining ionic solutions.