Chemical ReactionsChemical Reactions

9.3: Reactions in Aqueous 9.3: Reactions in Aqueous SolutionsSolutions

ObjectivesObjectivesDescribe aqueous solutions.Describe aqueous solutions.Write complete ionic and net ionic Write complete ionic and net ionic

equations for chemical reactions in equations for chemical reactions in aqueous solutions.aqueous solutions.

Predict whether reactions in aqueous Predict whether reactions in aqueous solutions will produce a precipitate, solutions will produce a precipitate, water, or a gas.water, or a gas.

A solution is a homogeneous mixture.

Solutes are the substances that are dissolved. The solvent is the substance that does the dissolving.

Water is the solvent in an aqueous solution.

Review

Aqueous SolutionsAqueous SolutionsThere can be many possible solutes

in an aqueous solution:

Ionic Compounds

DissolvesDoes not dissolve

Molecular Compounds

ReviewReviewWhen an When an ionic compoundionic compound dissolves in dissolves in

water, the ions in the compound will water, the ions in the compound will dissociatedissociate or separate from one or separate from one another. (See previous slide).another. (See previous slide).

When the solute is a When the solute is a molecular molecular compoundcompound, the molecules will not , the molecules will not come apart; they will simply exist as come apart; they will simply exist as separate molecules in solution. (See separate molecules in solution. (See previous slide)previous slide)

Recall that ionic compounds that Recall that ionic compounds that produce hydrogen ions when in produce hydrogen ions when in solution are called solution are called acidsacids..

Aqueous SolutionsAqueous Solutions

When two aqueous solutions of ionic When two aqueous solutions of ionic compounds combine (both solutions compounds combine (both solutions then contain then contain ionsions as solutes), as solutes), the the ions MAY reactions MAY react with one another. The with one another. The solvent (water) molecules do not solvent (water) molecules do not react.react.

Recall that these reactions are Recall that these reactions are double replacement reactions.double replacement reactions.3 types of products can form - a 3 types of products can form - a

precipitate, water, or a gas.precipitate, water, or a gas.

Precipitate ReactionsPrecipitate Reactions

2KI + Pb(NO3)2 2KNO3 + PbI2

The reaction in detail:The reaction in detail:

K+

NO3-

I-

NO3-

Pb+2

KI and Pb(NO3)2

exist as IONS!

PbI2 (the precipitate)

NO3- K+

K+I- K+

NO3-

Precipitate ReactionsPrecipitate Reactions

A chemical equation does not show A chemical equation does not show what is really going on - we need to what is really going on - we need to write an write an ionic equationionic equation to do that. to do that.A A completecomplete ionic equation shows all the ionic equation shows all the

particles in a solution as they really exist.particles in a solution as they really exist.

2K2K++ + 2I + 2I-- + Pb + Pb+2+2 + 2NO + 2NO33- - PbIPbI2 2 (s) + 2K(s) + 2K++ + +

2NO2NO33--

Practice ProblemPractice Problem

The reaction above produces a solid copper compound. Write a balanced chemical

equation and then a complete ionic equation.

Practice ProblemPractice Problem

The reaction above produces a solid copper compound. Write a balanced chemical

equation and then a complete ionic equation.

1. Na2CO3 + CuCl2 CuCO3 (s) + 2NaCl

2. 2Na+ + CO3-2 + Cu+2 + 2Cl-

CuCO3 (s) + 2Na+ + 2Cl-

Practice ProblemPractice ProblemA solution of silver nitrate and

sodium chloride are mixed and a compound containing silver

precipitates out. Write a balanced chemical equation and a complete

ionic equation for this reaction .

Practice Problem Practice Problem A solution of silver nitrate and

sodium chloride are mixed and a compound containing silver

precipitates out. Write a balanced chemical equation and a complete

ionic equation for this reaction.

1. AgNO3 + NaCl AgCl (s) + NaNO3

2. Ag+ + NO3- + Na+ + Cl-

AgCl (s) + Na+ + NO3

-

Spectator ionsSpectator ions

Notice that on both sides of this reaction there are ions that do NOT

participate in the reaction. These ions are called spectator ions.

Net Ionic EquationsNet Ionic Equations

To write a To write a net ionic equationnet ionic equation, cross , cross out all of the spectator ions. out all of the spectator ions. AgAg++ + Cl + Cl-- AgCl (s) AgCl (s)

Practice:Practice: 2K2K++ + 2I + 2I-- + Pb + Pb+2+2 + 2NO + 2NO33

- - PbIPbI22 + 2K + 2K++ + +

2NO2NO33

2Na2Na++ + CO + CO33-2-2 + Cu + Cu+2+2 + 2Cl + 2Cl--

CuCOCuCO33 (s) + 2Na (s) + 2Na++ + 2Cl + 2Cl--

                                                                                                           

                                                               

More Practice!More Practice!Write the chemical, complete ionic, Write the chemical, complete ionic,

and net ionic equations for the and net ionic equations for the precipitate reactions below.precipitate reactions below.Solutions of barium nitrate and sodium Solutions of barium nitrate and sodium

carbonate are mixed, forming the carbonate are mixed, forming the precipitate barium carbonate.precipitate barium carbonate.

Solutions of aluminum chloride and Solutions of aluminum chloride and sodium hydroxide are mixed, forming sodium hydroxide are mixed, forming the precipitate aluminum hydroxide.the precipitate aluminum hydroxide.

Reactions that form Reactions that form WaterWater

Another type of double-replacement Another type of double-replacement reaction that occurs in an aqueous reaction that occurs in an aqueous solution produces water molecules.solution produces water molecules.

Since water is colorless and odorless, Since water is colorless and odorless, there is no observable evidence that there is no observable evidence that a reaction occurred.a reaction occurred.HBr + NaOH NaBr + HHBr + NaOH NaBr + H22OO

HH++ + Br + Br-- + Na + Na++ + OH + OH-- Na Na++ + Br + Br--+ H+ H22OO

HH++ + OH + OH-- H H22O O

Practice ProblemsPractice Problems

Write the chemical, complete ionic, Write the chemical, complete ionic, and net ionic equations for the and net ionic equations for the reactions below, which all produce reactions below, which all produce water.water.sulfuric acid and potassium hydroxidesulfuric acid and potassium hydroxidephosphoric acid and magnesium phosphoric acid and magnesium

hydroxidehydroxidenitric acid and ammonium hydroxidenitric acid and ammonium hydroxide

Reactions that form GasesReactions that form Gases

A 3A 3rdrd type of double-replacement type of double-replacement reaction that occurs in aqueous reaction that occurs in aqueous solutions results in the formation of a solutions results in the formation of a gas.gas.

Common gases produced are:Common gases produced are:Carbon dioxide (COCarbon dioxide (CO22))Hydrogen cyanide (HCN)Hydrogen cyanide (HCN)Hydrogen sulfide (HHydrogen sulfide (H22S)S)

Practice ProblemsPractice Problems

Write the chemical, complete ionic, Write the chemical, complete ionic, and net ionic equations for the and net ionic equations for the reactions below, which all produce a reactions below, which all produce a gas.gas.Sulfuric acid reacts with sodium cyanideSulfuric acid reacts with sodium cyanideHydrochloric acid reacts with sodium Hydrochloric acid reacts with sodium

sulfidesulfideHydroiodic acid reacts with lithium Hydroiodic acid reacts with lithium

sulfidesulfide

COCO22 Production ProductionWhen you combine When you combine any acidic solution any acidic solution

and a carbonate and a carbonate (such as sodium (such as sodium hydrogen carbonate - aka sodium hydrogen carbonate - aka sodium bicarbonate or baking soda), 2 bicarbonate or baking soda), 2 reactions occur almost simultaneously.reactions occur almost simultaneously.

HCl + NaHCOHCl + NaHCO33 H H22COCO33 + NaCl + NaCl double replacementdouble replacement

HH22COCO33 H H22O (l) + COO (l) + CO22 (g) (g) decompositiondecomposition

COCO22 Production Production

By adding these 2 reactions, one By adding these 2 reactions, one chemical equation can be written.chemical equation can be written.

HCl + NaHCOHCl + NaHCO33 H H22COCO33 + NaCl + NaCl

HH22COCO33 H H22O (l) + COO (l) + CO22 (g) (g)

HCl + NaHCOHCl + NaHCO3 3 NaCl + HNaCl + H22O (l) + COO (l) + CO22 (g)(g)

COCO22 Production Production

Now take the overall equation and Now take the overall equation and write a complete ionic equation and write a complete ionic equation and a net ionic equation.a net ionic equation.HCl + NaHCOHCl + NaHCO3 3 NaCl + HNaCl + H22O (l) + COO (l) + CO22

(g)(g)

COCO22 Production Production

Now take the overall equation and Now take the overall equation and write a complete ionic equation and write a complete ionic equation and a net ionic equation.a net ionic equation.HCl + NaHCOHCl + NaHCO3 3 NaCl + HNaCl + H22O (l) + COO (l) + CO22

(g)(g)HH++ + Cl + Cl-- + Na + Na++ + HCO + HCO33

--

NaNa++ + Cl + Cl-- + H + H22O (l) + COO (l) + CO22 (g)(g)

HH++ + HCO + HCO33-- H H22O (l) + COO (l) + CO22 (g) (g)

Practice ProblemsPractice Problems

Write the chemical, complete ionic, Write the chemical, complete ionic, and net ionic equations for the and net ionic equations for the reactions below.reactions below.Perchloric acid (HClOPerchloric acid (HClO44) reacts with ) reacts with

potassium carbonatepotassium carbonateHydrobromic acid reacts with Hydrobromic acid reacts with

ammonium carbonateammonium carbonate