Reactions in Aqueous Solutions Prentice-Hall Chapter 11.3 Dr. Yager

Objectives Describe the information found in complete and net ionic equations. Predict the formation of a precipitate in a double-replacement reaction.

Structures in limestone caverns are formed when carbon dioxide converts calcium hydrogen carbonate into calcium carbonate. The calcium carbonate precipitates and forms dramatic stalactites and stalagmites. You will learn to predict the formation of precipitates and write equations to describe the reactions that produce them.

Net Ionic Equations Salts dissociate into cations and anions in water. Chemical reactions taking place in water are aqueous reactions. Standard Equation Complete Ionic Equation Net Ionic Equation

Complete Ionic Equation Standard Equation AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) Complete Ionic Equation Ag+(aq)+NO3-(aq)+Na+(aq)+Cl-(aq) AgCl(s)+Na+(aq)+NO3-(aq) The ions crossed out in red don’t participate

Ag+(aq) + Cl-(aq) AgCl(s) Spectator Ions Ag+(aq)+NO3-(aq)+Na+(aq)+Cl-(aq) AgCl(s)+Na+(aq)+NO3-(aq) The ions crossed out are called spectator ions. Ag+(aq) + Cl-(aq) AgCl(s) This is the net ionic equation and only shows particles directly involved in the chemical change.

An ion that appears on both sides of an equation and is not directly involved in the reaction is called a spectator ion. 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. It is balanced with respect to both mass and charge.

A Precipitate is Formed

Sodium ions and nitrate ions are not changed during the chemical reaction of silver nitrate and sodium chloride, so the net ionic equation is:

3Ca2+(aq) + 6OH-(aq) + 6H+ (aq) + 2PO43-(aq) Ca3(PO4)2(s) + 6H2O(l) This is both the complete and net ionic equation! (no spectator ions!)

Predicting the Formation of a Precipitate Precipitation can be predicted by the rules of solubility of ionic compounds. Solubility: How much solid will dissolve in a solution. When two ionic compounds are mixed, the cations can change partners. If the partners are insoluble, then they precipitate out of solution.

Remember these ions CO32- Carbonate PO43- Phosphate CrO42- Chromate S2- Sulfide OH- Hydroxide

Will a Precipitate Form? Sodium nitrate is soluble but carbonate is insoluble. The net ionic equation is

Will a Precipitate Form? Al2(SO4)3 + NH4OH ? CaCl2 + K2SO4 ?

Will a Precipitate Form? Al2(SO4)3 + NH4OH Al(OH)3(s) Yes

Remember these ions CO32- Carbonate PO43- Phosphate CrO42- Chromate S2- Sulfide OH- Hydroxide

Will a Precipitate Form? Al2(SO4)3 + NH4OH Al(OH)3(s) Yes CaCl2 + K2SO4 CaSO4(s) Yes

What Happens? Ag(NO3) and Na2SO4 NH4Cl and Ba(NO3)2 Pb(NO3)2 and HCl

What Happens? Ag(NO3) and Na2SO4 Ag2(SO4)(s) ppt NH4Cl and Ba(NO3)2 Pb(NO3)2 and HCl Ag2(SO4)(s) ppt

Remember these ions CO32- Carbonate PO43- Phosphate CrO42- Chromate S2- Sulfide OH- Hydroxide

What Happens? Ag(NO3) and Na2SO4 Ag2(SO4)(s) ppt NH4Cl and Ba(NO3)2 Pb(NO3)2 and HCl Nothing

What Happens? Ag(NO3) and Na2SO4 Ag2(SO4)(s) ppt NH4Cl and Ba(NO3)2 Nothing Pb(NO3)2 and HCl PbCl2(s) ppt

FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq) Identify the correct net ionic equation for the following reaction and the spectator ions, if they exist. FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq) Fe2+(aq) + O2-(aq) + 2H+(aq) + 2ClO4-(aq)  H2O(l) + Fe2+(aq) + 2ClO4-(aq); no spectator ion O2-(aq) + 2H+(aq)  H2O(l); Fe2+ and ClO4- are spectator ions FeO(aq) + 2H+(aq)  H2O(l) + Fe2+(aq); ClO4- is the spectator ion FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq); no spectator ion

FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq) Identify the correct net ionic equation for the following reaction and the spectator ions, if they exist. FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq) Fe2+(aq) + O2-(aq) + 2H+(aq) + 2ClO4-(aq)  H2O(l) + Fe2+(aq) + 2ClO4-(aq); no spectator ion O2-(aq) + 2H+(aq)  H2O(l); Fe2+ and ClO4- are spectator ions FeO(aq) + 2H+(aq)  H2O(l) + Fe2+(aq); ClO4- is the spectator ion FeO(aq) + 2HClO4(aq)  H2O(l) + Fe(ClO4)2(aq); no spectator ion

2. Which one of the following products of double-replacement reactions would NOT form a precipitate? AgCl PbSO4 Mg(OH)2 Mo(NO3)2

2. Which one of the following products of double-replacement reactions would NOT form a precipitate? AgCl PbSO4 Mg(OH)2 Mo(NO3)2

3. Which reaction will NOT produce a precipitate from aqueous solution? Hg2(NO3)2 + KCl FeSO4 + Ba(OH)2 Pb(NO3)2 + Na2CO3 NaBr + Al2(SO4)2

3. Which reaction will NOT produce a precipitate from aqueous solution? Hg2(NO3)2 + KCl FeSO4 + Ba(OH)2 Pb(NO3)2 + Na2CO3 NaBr + Al2(SO4)2

Colors of Some Common Water-Insoluble Materials Carbonates, CO32- Ag2CO3 = yellow CuCO3 = pale blue BaCO3 = white CaCO3 = white Chlorides, Cl- AgCl = white Hg2Cl2 = white PbCl2 = white CuCl = white Hydroxides, OH- AgOH = grey-brown Cu(OH)2 = pale blue Fe(OH)3= rust red Ni(OH)2 = pale green Pb(OH)2= white Zn(OH)2 = white Iodides, I- AgI = yellow Hg2I2 = yellow-orange PbI2 = yellow CuI = brown Sulfides, S2- Ag2S = black CuS = black Fe2S3 = black HgS = black NiS = black PbS = black Sulfates, SO42- BaSO4 = white PbSO4 = white