Unit 1 – reactions in aqueous solutions Lesson 2 Chemistry 40S Unit 1 – reactions in aqueous solutions Lesson 2

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: 0C 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.