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?