11.3 Reactions in Aqueous Solution 1 > Chapter 11 Chemical Reactions 11.1 Describing Chemical Reactions 11.2 Types of Chemical Reactions 11.3 Reactions in Aqueous Solution Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 2 > Net Ionic Equations Your world is water based. More than 70 percent of Earth’s surface is covered by water, and about 66 percent of the adult human body is water. Thus, many important chemical reactions take place in water—that is, in aqueous solution. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 3 > Net Ionic Equations The reaction of aqueous solutions of silver nitrate and sodium chloride to form solid silver chloride and aqueous sodium nitrate is a double- replacement reaction. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. AgNO 3 (aq) + NaCl(aq) → AgCl(s) + NaNO 3 (aq)

11.3 Reactions in Aqueous Solution 4 > Net Ionic Equations The equation does not show that, like most ionic compounds, the reactants and one of the products dissociate, or separate, into cations and anions when they dissolve in water. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. AgNO 3 (aq) + NaCl(aq) → AgCl(s) + NaNO 3 (aq)

11.3 Reactions in Aqueous Solution 5 > Net Ionic Equations Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. AgNO 3 (aq) + NaCl(aq) → AgCl(s) + NaNO 3 (aq) When sodium chloride dissolves in water, it separates into sodium ions (Na + (aq)) and chloride ions (Cl – (aq)).

11.3 Reactions in Aqueous Solution 6 > Net Ionic Equations Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. AgNO 3 (aq) + NaCl(aq) → AgCl(s) + NaNO 3 (aq) When sodium chloride dissolves in water, it separates into sodium ions (Na + ) and chloride ions (Cl – ). When dissolved in water, silver nitrate dissociates into silver ions (Ag + ) and nitrate ions (NO 3 – ).

11.3 Reactions in Aqueous Solution 7 > Net Ionic Equations Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Ag + (aq) + NO 3 – (aq) + Na + (aq) + Cl – (aq) → AgCl(s) + Na + (aq) + NO 3 – (aq) You can use these ions to write a complete ionic equation, an equation that shows dissolved ionic compounds as dissociated free ions.

11.3 Reactions in Aqueous Solution 8 > Net Ionic Equations Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Notice that the nitrate ion and the sodium ion appear unchanged on both sides of the equation. The equation can be simplified by eliminating these ions because they don’t participate in the reaction. Ag + (aq) + NO 3 – (aq) + Na + (aq) + Cl – (aq) → AgCl(s) + Na + (aq) + NO 3 – (aq)

11.3 Reactions in Aqueous Solution 9 > An ion that appears on both sides of an equation and is not directly involved in the reaction is called a spectator ion. When you rewrite an equation leaving out the spectator ions, you have the net ionic equation. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations Ag + (aq) + NO 3 – (aq) + Na + (aq) + Cl – (aq) → AgCl(s) + Na + (aq) + NO 3 – (aq)

11.3 Reactions in Aqueous Solution 10 > The net ionic equation is an equation for a reaction in solution that shows only those particles that are directly involved in the chemical change. Ag + (aq) + Cl – (aq) → AgCl(s) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations

11.3 Reactions in Aqueous Solution 11 > In writing balanced net ionic equations, you must make sure that the ionic charge is balanced. The net ionic charge on each side of the equation is zero and is therefore balanced. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations Ag + (aq) + Cl – (aq) → AgCl(s)

11.3 Reactions in Aqueous Solution 12 > Consider the skeleton equation for the reaction of lead with silver nitrate. Pb(s) + AgNO 3 (aq) → Ag(s) + Pb(NO 3 ) 2 (aq) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations

11.3 Reactions in Aqueous Solution 13 > Consider the skeleton equation for the reaction of lead with silver nitrate. Pb(s) + AgNO 3 (aq) → Ag(s) + Pb(NO 3 ) 2 (aq) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations The nitrate ion is the spectator ion in this reaction. The net ionic equation is as follows: Pb(s) + Ag + (aq) → Ag(s) + Pb 2+ (aq) (unbalanced)

11.3 Reactions in Aqueous Solution 14 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations Placing the coefficient 2 in front of Ag + (aq) balances the charge. Pb(s) + 2Ag + (aq) → 2Ag(s) + Pb 2+ (aq) (balanced)

11.3 Reactions in Aqueous Solution 15 > A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations

11.3 Reactions in Aqueous Solution 16 > A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge. Only single- and double-replacement reactions can be written as net ionic equations. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Net Ionic Equations

11.3 Reactions in Aqueous Solution 17 > Sample Problem 11.8 Writing and Balancing Net Ionic Equations Aqueous solutions of iron(III) chloride and potassium hydroxide are mixed. A precipitate of iron(III) hydroxide forms. Identify the spectator ions and write a balanced net ionic equation for the reaction. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 18 > Solve Apply concepts to this problem. 2 Write the complete ionic equation for the reaction, showing soluble ionic compounds as individual ions. Fe 3+ (aq) + 3Cl – (aq) + 3K + (aq) + 3OH – (aq) → Fe(OH) 3 (s) + 3K + (aq) + 3Cl – (aq) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.8

11.3 Reactions in Aqueous Solution 19 > Fe 3+ (aq) + 3Cl – (aq) + 3K + (aq) + 3OH – (aq) → Fe(OH) 3 (s) + 3K + (aq) + 3Cl – (aq) Solve Apply concepts to this problem. 2 Eliminate aqueous ions that appear as both reactants and products. The spectator ions are K + and Cl –. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.8

11.3 Reactions in Aqueous Solution 20 > Solve Apply concepts to this problem. 2 Balance the net ionic equation. Fe 3+ (aq) + 3OH – (aq) → Fe(OH) 3 (s) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.8

11.3 Reactions in Aqueous Solution 21 > What is the difference between complete ionic equations and net ionic equations? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 22 > What is the difference between complete ionic equations and net ionic equations? Complete ionic equations show all ions present in solution during a reaction. Net ionic equations show only those ions that are directly involved in the reaction. Ions that do not participate, known as spectator ions, are not shown in a net ionic equation. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 23 > Predicting the Formation of a Precipitate How can you predict the formation of a precipitate in a double-replacement reaction? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 24 > You have seen that mixing solutions of two ionic compounds can sometimes result in the formation of an insoluble salt called a precipitate. Some combinations of solutions produce precipitates, while others do not. Whether or not a precipitate forms depends upon the solubility of the new compounds that form. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate

11.3 Reactions in Aqueous Solution 25 > By using the general rules for solubility of ionic compounds, you can predict the formation of a precipitate. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate

11.3 Reactions in Aqueous Solution 26 > Solubility Rules for Ionic Compounds CompoundsSolubilityExceptions Salts of alkali metals and ammonia SolubleSome lithium compounds Nitrate salts and chlorate salts SolubleFew exceptions Sulfate saltsSoluble Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chloride saltsSoluble Compounds of Ag and some compounds of Hg and Pb Carbonates, phosphates, chromates, sulfides, and hydroxides Most are insoluble Compounds of the alkali metals and of ammonia Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Interpret Data

11.3 Reactions in Aqueous Solution 27 > Will a precipitate form when aqueous solutions of Na 2 CO 3 (aq) and Ba(NO 3 ) 2 (aq) are mixed? 2Na + (aq) + CO 3 2– (aq) + Ba 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate

11.3 Reactions in Aqueous Solution 28 > Will a precipitate form when aqueous solutions of Na 2 CO 3 (aq) and Ba(NO 3 ) 2 (aq) are mixed? 2Na + (aq) + CO 3 2– (aq) + Ba 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate When these four ions are mixed, the cations could change partners.

11.3 Reactions in Aqueous Solution 29 > Will a precipitate form when aqueous solutions of Na 2 CO 3 (aq) and Ba(NO 3 ) 2 (aq) are mixed? 2Na + (aq) + CO 3 2– (aq) + Ba 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate The two new compounds that would form are NaNO 3 and BaCO 3. –These are the only new combinations of cation and anion possible.

11.3 Reactions in Aqueous Solution 30 > Will a precipitate form when aqueous solutions of Na 2 CO 3 (aq) and Ba(NO 3 ) 2 (aq) are mixed? 2Na + (aq) + CO 3 2– (aq) + Ba 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate To find out if an exchange will occur, refer to the solubility rules for ionic compounds. –Sodium nitrate will not form a precipitate because alkali metal salts and nitrate salts are soluble. –Carbonates in general are insoluble. Barium carbonate will precipitate.

11.3 Reactions in Aqueous Solution 31 > Will a precipitate form when aqueous solutions of Na 2 CO 3 (aq) and Ba(NO 3 ) 2 (aq) are mixed? 2Na + (aq) + CO 3 2– (aq) + Ba 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Predicting the Formation of a Precipitate In this reaction, Na + and NO 3 – are spectator ions. The net ionic equation for this reaction is: Ba 2+ (aq) + CO 3 2– (aq) → BaCO 3 (s)

11.3 Reactions in Aqueous Solution 32 > CHEMISTRY & YOU How did the soda straws, which are composed of calcium carbonate, get into the cave? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 33 > CHEMISTRY & YOU How did the soda straws, which are composed of calcium carbonate, get into the cave? Soda straws form when there is calcium carbonate dissolved in water that drips very slowly from the ceiling of the cave. Because calcium carbonate is not very soluble, it comes out of solution and forms “soda straws” made of calcium carbonate. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 34 > Sample Problem 11.9 Writing and Balancing Net Ionic Equations Aqueous potassium carbonate reacts with aqueous strontium nitrate. Identify the precipitate formed and write the net ionic equation for the reaction. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

11.3 Reactions in Aqueous Solution 35 > Solve Apply concepts to this situation. 2 Write the reactants, showing each as dissociated free ions. 2K + (aq) + CO 3 2– (aq) + Sr 2+ (aq) + 2NO 3 – (aq) → ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.9

11.3 Reactions in Aqueous Solution 36 > Solve Apply concepts to this situation. 2 Of the two possible combinations, KNO 3 is soluble and SrCO 3 is insoluble. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.9 Use the solubility rules to identify the precipitate formed.

11.3 Reactions in Aqueous Solution 37 > Solve Apply concepts to this situation. 2 Eliminate the spectator ions and write the net ionic equation. CO 3 2– (aq) + Sr 2+ (aq) → SrCO 3 (s) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 11.9

11.3 Reactions in Aqueous Solution 38 > END OF 11.3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.