AP Notes Chapter 5AP Notes Chapter 5Reactions in Aqueous SolutionsReactions in Aqueous Solutions

Parts of SolutionsParts of Solutions

Solution- homogeneous mixture.Solution- homogeneous mixture. Solute- what gets dissolved.Solute- what gets dissolved. Solvent- what does the dissolving.Solvent- what does the dissolving. Soluble- Can be dissolved.Soluble- Can be dissolved. Miscible- liquids dissolve in each Miscible- liquids dissolve in each

other.other.

Aqueous solutionsAqueous solutions Dissolved in water.Dissolved in water. Water is a good solvent Water is a good solvent

because the molecules are because the molecules are polar.polar.

The oxygen atoms have a The oxygen atoms have a partial negative charge.partial negative charge.

The hydrogen atoms have a The hydrogen atoms have a partial positive charge.partial positive charge.

The angle is 105ºC.The angle is 105ºC.

HydrationHydration

The process of breaking the ions of The process of breaking the ions of salts apart. salts apart.

Ions have charges and attract the Ions have charges and attract the opposite charges on the water opposite charges on the water molecules. molecules.

HydrationHydration

H HOH

H OH

HO

H HO

HHO

HH

O

HH

OH

H

O

HH

O

SolubilitySolubility How much of a substance will dissolve How much of a substance will dissolve

in a given amount of water.in a given amount of water. Usually g/100 mLUsually g/100 mL Varies greatly, but if they do dissolve Varies greatly, but if they do dissolve

the ions are separated,the ions are separated, and they can move around.and they can move around. Water can also dissolve non-ionic Water can also dissolve non-ionic

compounds if they have polar bonds.compounds if they have polar bonds.

ElectrolytesElectrolytes

Electricity is moving charges.Electricity is moving charges. The ions that are dissolved can The ions that are dissolved can

move.move. Solutions of ionic compounds can Solutions of ionic compounds can

conduct electricity.conduct electricity. Electrolytes.Electrolytes. Solutions are classified three ways. Solutions are classified three ways.

Types of solutionsTypes of solutions Strong electrolytesStrong electrolytes- completely - completely

dissociate (fall apart into ions).dissociate (fall apart into ions). Many ions- Conduct well.Many ions- Conduct well. Weak electrolytesWeak electrolytes- Partially fall apart - Partially fall apart

into ions.into ions. Few ions -Conduct electricity slightly.Few ions -Conduct electricity slightly. Non-electrolytesNon-electrolytes- Don’t fall apart.- Don’t fall apart. No ions- Don’t conduct.No ions- Don’t conduct.

Types of solutionsTypes of solutions Acids- form HAcids- form H++ ions when dissolved. ions when dissolved. Strong acids fall apart completely.Strong acids fall apart completely. many ionsmany ions HH22SOSO44 HNO HNO33 HCl HBr HI HClO HCl HBr HI HClO44 Weak acids- don’t dissociate completely.Weak acids- don’t dissociate completely. Bases - form OHBases - form OH-- ions when dissolved. ions when dissolved. Strong bases- many ions.Strong bases- many ions. KOH NaOHKOH NaOH

Measuring SolutionsMeasuring Solutions Concentration- how much is dissolved.Concentration- how much is dissolved. Molarity = Moles of soluteMolarity = Moles of solute

Liters of solution Liters of solution abbreviated Mabbreviated M 1 M = 1 mol solute / 1 liter solution1 M = 1 mol solute / 1 liter solution Calculate the molarity of a solution with Calculate the molarity of a solution with

34.6 g of NaCl dissolved in 125 mL of 34.6 g of NaCl dissolved in 125 mL of solution. solution.

MolarityMolarity

How many grams of HCl would be How many grams of HCl would be required to make 50.0 mL of a 2.7 M required to make 50.0 mL of a 2.7 M solution?solution?

What would the concentration be if What would the concentration be if you used 27g of CaClyou used 27g of CaCl22 to make 500. to make 500.

mL of solution?mL of solution? What is the concentration of each ion?What is the concentration of each ion?

MolarityMolarity

Calculate the concentration of a Calculate the concentration of a solution made by dissolving 45.6 g of solution made by dissolving 45.6 g of FeFe22(SO(SO44))33 to 475 mL. to 475 mL.

What is the concentration of each What is the concentration of each ion?ion?

Making solutionsMaking solutions

Describe how to make 100.0 mL of a Describe how to make 100.0 mL of a 1.0 M K1.0 M K22CrCr22OO44 solution. solution.

Describe how to make 250. mL of an Describe how to make 250. mL of an 2.0 M copper (II) sulfate dihydrate 2.0 M copper (II) sulfate dihydrate solution.solution.

DilutionDilution Adding more solvent to a known Adding more solvent to a known

solution.solution. The moles of solute stay the same.The moles of solute stay the same. moles = M x Lmoles = M x L MM11 VV11 = M = M22 VV22 moles = molesmoles = moles

Stock solutionStock solution is a solution of known is a solution of known concentration used to make more concentration used to make more dilute solutionsdilute solutions

DilutionDilution What volume of a 1.7 M solutions is What volume of a 1.7 M solutions is

needed to make 250 mL of a 0.50 M needed to make 250 mL of a 0.50 M solution?solution?

18.5 mL of 2.3 M HCl is added to 250 18.5 mL of 2.3 M HCl is added to 250 mL of water. What is the concentration mL of water. What is the concentration of the solution?of the solution?

18.5 mL of 2.3 M HCl is diluted to 250 18.5 mL of 2.3 M HCl is diluted to 250 mL with water. What is the mL with water. What is the concentration of the solution?concentration of the solution?

DilutionDilution

You have a 4.0 M stock solution. You have a 4.0 M stock solution. Describe how to make 1.0L of a .75 Describe how to make 1.0L of a .75 M solution.M solution.

25 mL 0.67 M of H25 mL 0.67 M of H22SOSO44 is added to is added to

35 mL of 0.40 M CaCl35 mL of 0.40 M CaCl22 . What mass . What mass

CaSOCaSO44 Is formed? Is formed?

Types of ReactionsTypes of Reactions

1 Precipitation reactions1 Precipitation reactions When aqueous solutions of ionic When aqueous solutions of ionic

compounds are poured together a compounds are poured together a solid forms. solid forms.

A solid that forms from mixed A solid that forms from mixed solutions is a precipitatesolutions is a precipitate

If you’re not a part of the solution, If you’re not a part of the solution, your part of the precipitate your part of the precipitate

Precipitation ReactionsPrecipitation Reactions NaOH(aq)+FeClNaOH(aq)+FeCl33(aq) (aq) NaCl(aq) + NaCl(aq) +

Fe(OH)Fe(OH)33(s)(s)

is reallyis really

NaNa++(aq)+OH(aq)+OH--(aq) + Fe(aq) + Fe+3+3 + Cl + Cl--(aq) (aq) NaNa++ (aq) + Cl (aq) + Cl-- (aq) + Fe(OH) (aq) + Fe(OH)33(s)(s)

So all that really happens isSo all that really happens is

OHOH--(aq) + Fe(aq) + Fe+3+3 Fe(OH) Fe(OH)33(s)(s)

Double replacement reactionDouble replacement reaction

Precipitation ReactionPrecipitation Reaction

We can predict the productsWe can predict the products Can only be certain by experimentingCan only be certain by experimenting The anion and cation switch partnersThe anion and cation switch partners

AgNOAgNO33((aqaq) + KCl() + KCl(aqaq) )

Zn(NOZn(NO33))22((aqaq) + BaCr) + BaCr22OO77((aqaq) )

CdClCdCl22((aqaq) + Na) + Na22S(S(aqaq) )

Precipitations ReactionsPrecipitations Reactions

Only happen if one of the products is Only happen if one of the products is insolubleinsoluble

Otherwise all the ions stay in Otherwise all the ions stay in solution- nothing has happened.solution- nothing has happened.

Need to memorize the rules for Need to memorize the rules for solubility (pg 151)solubility (pg 151)

http://www.fairbornchempage.com/Resources/solubility.htm

Solubility RulesSolubility Rules All nitrates are solubleAll nitrates are soluble Alkali metals ions and NHAlkali metals ions and NH44

++ ions are soluble ions are soluble

Halides are soluble except AgHalides are soluble except Ag++, Pb, Pb+2+2, Hg, Hg22+2+2

Most sulfates are soluble, except PbMost sulfates are soluble, except Pb+2+2, Ba, Ba+2+2, , HgHg+2+2,and Ca,and Ca+2+2

Most hydroxides are slightly soluble (insoluble) Most hydroxides are slightly soluble (insoluble) except NaOH and KOHexcept NaOH and KOH

Sulfides, carbonates, chromates, and phosphates Sulfides, carbonates, chromates, and phosphates are insolubleare insoluble

Lower number rules supersede so NaLower number rules supersede so Na22S is solubleS is soluble

Three Types of EquationsThree Types of Equations

Molecular EquationMolecular Equation- written as whole - written as whole formulas, not the ions.formulas, not the ions.

KK22CrOCrO44((aqaq) + Ba(NO) + Ba(NO33))22((aqaq) ) Complete Ionic equation Complete Ionic equation show dissolved show dissolved

electrolytes as the ions.electrolytes as the ions. 2K2K++ + CrO + CrO44

-2-2 + Ba + Ba+2+2 + 2 NO + 2 NO33--

BaCrO BaCrO44(s)(s) + 2K+ 2K++ + 2 NO + 2 NO33--

Spectator ions Spectator ions are those that don’t react.are those that don’t react.

Three Type of EquationsThree Type of Equations Net Ionic equationsNet Ionic equations show only those show only those

ions that react, not the spectator ionsions that react, not the spectator ions BaBa+2+2 + CrO + CrO44

-2-2 BaCrO BaCrO44(s)(s)

Write the three types of equations for Write the three types of equations for the reactions when these solutions are the reactions when these solutions are mixed.mixed.

Iron (III) sulfate and potassium sulfide Iron (III) sulfate and potassium sulfide Lead (II) nitrate and sulfuric acid.Lead (II) nitrate and sulfuric acid.

Stoichiometry of Stoichiometry of PrecipitationPrecipitation Exactly the same, except you may have Exactly the same, except you may have

to figure out what the pieces are.to figure out what the pieces are. What mass of solid is formed when What mass of solid is formed when

100.00 mL of 0.100 M Barium chloride 100.00 mL of 0.100 M Barium chloride is mixed with 100.00 mL of 0.100 M is mixed with 100.00 mL of 0.100 M sodium hydroxide?sodium hydroxide?

What volume of 0.204 M HCl is needed What volume of 0.204 M HCl is needed to precipitate the silver from 50.ml of to precipitate the silver from 50.ml of 0.0500 M silver nitrate solution ?0.0500 M silver nitrate solution ?

Types of ReactionsTypes of Reactions2 Acid-Base2 Acid-Base For our purposes an acid is a proton For our purposes an acid is a proton

donor.donor. a base is a proton acceptor usually OHa base is a proton acceptor usually OH--

What is the net ionic equation for the What is the net ionic equation for the reaction of HCl(aq) and KOH(aq)?reaction of HCl(aq) and KOH(aq)?

Acid + Base Acid + Base salt + water salt + water HH++ + OH + OH-- H H22OO

Acid - Base ReactionsAcid - Base Reactions Often called a neutralization reaction Often called a neutralization reaction

Because the acid neutralizes the base.Because the acid neutralizes the base. Often titrate to determine Often titrate to determine

concentrations.concentrations. Solution of known concentration Solution of known concentration

(titrant),(titrant), is added to the unknown (analyte),is added to the unknown (analyte), until the equivalence point is reached until the equivalence point is reached

where enough titrant has been added where enough titrant has been added to neutralize it. to neutralize it.

TitrationTitration Where the indicator changes color is the Where the indicator changes color is the

endpoint.endpoint. Not always at the equivalence point.Not always at the equivalence point. A 50.00 mL sample of aqueous Ca(OH)A 50.00 mL sample of aqueous Ca(OH)22

requires 34.66 mL of 0.0980 M Nitric requires 34.66 mL of 0.0980 M Nitric acid for neutralization. What is [Ca(OH)acid for neutralization. What is [Ca(OH)22

]? ]? # of H# of H++ x M x MA A x Vx VA A = = # of OH# of OH-- x M x MB B x Vx VBB

MVMVacidacid = MV = MVbasebase

IndicatorsIndicators

Acid-Base ReactionAcid-Base Reaction

75 mL of 0.25M HCl is mixed with 75 mL of 0.25M HCl is mixed with 225 mL of 0.055 M Ba(OH)225 mL of 0.055 M Ba(OH)22 . What is . What is

the concentration of the excess Hthe concentration of the excess H++ or or OHOH-- ? ?

Types of ReactionTypes of Reaction

3 Oxidation-Reduction called Redox3 Oxidation-Reduction called Redox Ionic compounds are formed through Ionic compounds are formed through

the transfer of electrons.the transfer of electrons. An Oxidation-reduction reaction An Oxidation-reduction reaction

involves the transfer of electrons.involves the transfer of electrons. We need a way of keeping track.We need a way of keeping track.

                        Activity SeriesMetals (Decreasing Activity)

LiK

BaSrCaNa

  Lithium  Potassium  Barium  Strontium  Calcium  Sodium

 

Gives Off H2

From H2O

Gives Off H2

From Acids

  Never Found Free In Nature Mg

AlMnZnCr

  Magnesium  Aluminum  Manganese  Zinc  Chromium

 

FeCdCoNiSnPb

  Iron  Cadmium  Cobalt  Nickel  Tin  Lead

DecreasingActivity

&Increasing

Electronegativity

Decreasing Activity

Rarely Found Free In Nature

H   Hydrogen  

CuArBiSbHgAgPtAu

 Copper  Arsenic  Bismuth  Antimony  Mercury  Silver  Platinum  Gold

   Found Free In

Nature

http://www.fairbornchempage.com/Resources/activity.htm

F2

Cl2Br2

I2

Fluorine2

  Chlorine2

  Bromine2

  Iodine2

Decreasing Decreasing ActivityActivity

                        Activity SeriesHalogens (Decreasing Activity)

Oxidation StatesOxidation States A way of keeping track of the electrons.A way of keeping track of the electrons. Not necessarily true of what is in Not necessarily true of what is in

nature, but it works.nature, but it works. need the rules for assigning need the rules for assigning

(memorize).(memorize).

The oxidation state of elements in their The oxidation state of elements in their standard states is zero.standard states is zero.

Oxidation state for monoatomic ions Oxidation state for monoatomic ions are the same as their charge.are the same as their charge.

Oxidation StatesOxidation States Oxygen is assigned an oxidation state Oxygen is assigned an oxidation state

of -2 in its covalent compounds except of -2 in its covalent compounds except as a peroxide.as a peroxide.

In compounds with nonmetals hydrogen In compounds with nonmetals hydrogen is assigned the oxidation state +1.is assigned the oxidation state +1.

In its compounds fluorine is always –1.In its compounds fluorine is always –1. The sum of the oxidation states must be The sum of the oxidation states must be

zero in compounds or equal the charge zero in compounds or equal the charge of the ion.of the ion.

Oxidation StatesOxidation States Assign the oxidation states to each Assign the oxidation states to each

element in the following.element in the following. COCO22

NONO33--

HH22SOSO44

FeFe22OO33

FeFe33OO44

Oxidation-ReductionOxidation-Reduction Transfer electrons, so the oxidation Transfer electrons, so the oxidation

states change.states change. 2Na + Cl2Na + Cl22 2NaCl 2NaCl CHCH44 + 2O + 2O22 CO CO22 + 2H + 2H22OO Oxidation is the loss of electrons.Oxidation is the loss of electrons. Reduction is the gain of electrons.Reduction is the gain of electrons. OIL RIG oxidation is losing and OIL RIG oxidation is losing and

reduction is gainingreduction is gaining LEO “the lion says” GERLEO “the lion says” GER

lose electron oxidationlose electron oxidationgain electron reductiongain electron reduction

Oxidation-ReductionOxidation-Reduction Oxidation means an increase in Oxidation means an increase in

oxidation state - lose electrons.oxidation state - lose electrons. Reduction means a decrease in Reduction means a decrease in

oxidation state - gain electrons.oxidation state - gain electrons. The substance that is oxidized is The substance that is oxidized is

called the reducing agent.called the reducing agent. The substance that is reduced is The substance that is reduced is

called the oxidizing agent.called the oxidizing agent.

Redox ReactionsRedox Reactions

AgentsAgents Oxidizing agent gets reduced.Oxidizing agent gets reduced. Gains electrons.Gains electrons. More negative oxidation state.More negative oxidation state. Reducing agent gets oxidized.Reducing agent gets oxidized. Loses electrons.Loses electrons. More positive oxidation state.More positive oxidation state.

Identify the Identify the Oxidizing agentOxidizing agent Reducing agentReducing agent Substance oxidizedSubstance oxidized Substance reducedSubstance reduced in the following reactionsin the following reactions FeFe ((ss) + O) + O22((gg) ) Fe Fe22OO33((ss) ) FeFe22OO33((ss)+ 3 CO()+ 3 CO(gg) ) 2 Fe( 2 Fe(ll) + 3 CO) + 3 CO22((gg)) SOSO33

-- + H + H++ + MnO + MnO44- - SO SO44

-- + H + H22O + MnO + Mn+2+2

Half-ReactionsHalf-Reactions All redox reactions can be thought of as All redox reactions can be thought of as

happening in two halves.happening in two halves. One produces electrons - Oxidation half.One produces electrons - Oxidation half. The other requires electrons - Reduction half.The other requires electrons - Reduction half. Write the half reactions for the following.Write the half reactions for the following.

Na + ClNa + Cl22 Na Na++ + Cl + Cl--

Na Na Na Na++ + 1e- (LEO) Cl + 1e- (LEO) Cl22 + 2e- + 2e- 2Cl 2Cl- - (GER)(GER)

SOSO33-2-2 + H + H++ + MnO + MnO44

- - SO SO44-2-2 + H + H22O + MnO + Mn+2+2

SOSO33-2-2 SO SO44

-2-2 + 2e- (LEO) + 2e- (LEO)

MnOMnO44- - + 5e- + 5e- Mn Mn+2 +2 (GER)(GER)

Balancing Redox EquationsBalancing Redox Equations In aqueous solutions the key is the In aqueous solutions the key is the

number of electrons produced must be number of electrons produced must be the same as those required.the same as those required.

For reactions in acidic solution an 8 step For reactions in acidic solution an 8 step procedure.procedure.

Write separate half reactionsWrite separate half reactions For each half reaction balance all For each half reaction balance all

reactants except H and Oreactants except H and O Balance O using HBalance O using H22OO

Acidic SolutionAcidic Solution Balance H using HBalance H using H++

Balance charge using eBalance charge using e-- Multiply equations to make electrons Multiply equations to make electrons

equalequal Add equations and cancel identical Add equations and cancel identical

speciesspecies Check that charges and elements are Check that charges and elements are

balanced.balanced.

PracticePractice The following reactions occur in aqueous The following reactions occur in aqueous

solution. Balance themsolution. Balance them Cr(OH)Cr(OH)33 + OCl + OCl-- + OH + OH-- CrOCrO44

-2-2 + Cl + Cl-- + H + H22OO

MnOMnO44-- + Fe + Fe+2+2 MnMn+2+2 + Fe + Fe+3+3

Cu + NOCu + NO33-- Cu Cu+2+2 + NO(g)+ NO(g)

Pb + PbOPb + PbO22 + SO + SO44-2-2 PbSO PbSO44

MnMn+2+2 + NaBiO+ NaBiO33 Bi Bi+3+3 + MnO+ MnO44--

Now for a tough oneNow for a tough oneFe(CN)Fe(CN)66

-4-4 + MnO + MnO44-- MnMn+2+2 + Fe+ Fe+3+3 + + COCO2 2 + +

NONO33--

Basic SolutionBasic Solution Do everything you would with acid, Do everything you would with acid,

but add one more step.but add one more step. Add enough OHAdd enough OH-- to both sides to to both sides to

neutralize the Hneutralize the H++

CrICrI33 + Cl + Cl22 CrO CrO44-- + IO+ IO44

-- + Cl + Cl--

Fe(OH)Fe(OH)22 + H + H22OO22 Fe(OH) Fe(OH)--

Redox TitrationsRedox Titrations Same as any other titration.Same as any other titration. The permanganate ion is used often The permanganate ion is used often

because it is its own indicator. MnObecause it is its own indicator. MnO44-- is is

purple, Mnpurple, Mn+2+2 is colorless. When reaction is colorless. When reaction solution remains clear, MnOsolution remains clear, MnO44

-- is gone. is gone.

Chromate ion is also useful, but color Chromate ion is also useful, but color change, orangish yellow to green, is change, orangish yellow to green, is harder to detect.harder to detect.

ExampleExample The iron content of iron ore can be The iron content of iron ore can be

determined by titration with standard determined by titration with standard KMnOKMnO44 solution. The iron ore is dissolved in solution. The iron ore is dissolved in

excess HCl, and the iron reduced to Feexcess HCl, and the iron reduced to Fe+2+2 ions. This solution is then titrated with ions. This solution is then titrated with KMnOKMnO44 solution, producing Fe solution, producing Fe+3+3 and Mn and Mn+2+2

ions in acidic solution. If it requires 41.95 ions in acidic solution. If it requires 41.95 mL of 0.205 M KMnOmL of 0.205 M KMnO44 to titrate a solution to titrate a solution

made with 0.6128 g of iron ore, what made with 0.6128 g of iron ore, what percent of the ore was iron?percent of the ore was iron?