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8/10/2019 AP Chemistry Chapter 4 Powerpoint
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AqueousReactions
2009, Prentice-Hall, Inc.
Chapter 4 Aqueous Reactions and
Solution Stoichiometry
John D. Bookstaver
St. Charles Community CollegeCottleville, MO
Chemistry, The Central Science , 11th editionTheodore L. Brown; H. Eugene LeMay, Jr.;
and Bruce E. Bursten
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8/10/2019 AP Chemistry Chapter 4 Powerpoint
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AqueousReactions
2009, Prentice-Hall, Inc.
Dissociation
When an ionicsubstance dissolves
in water, the solventpulls the individualions from the crystaland solvates them.
This process is calleddissociation .
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AqueousReactions
2009, Prentice-Hall, Inc.
Dissociation
An electrolyte is asubstances that
dissociates into ionswhen dissolved inwater.
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AqueousReactions
2009, Prentice-Hall, Inc.
Electrolytes
An electrolyte is asubstances that
dissociates into ionswhen dissolved inwater.
A nonelectrolyte maydissolve in water, butit does not dissociateinto ions when it doesso.
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AqueousReactions
2009, Prentice-Hall, Inc.
Electrolytes andNonelectrolytes
Soluble ioniccompounds tendto be electrolytes.
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AqueousReactions
2009, Prentice-Hall, Inc.
Electrolytes andNonelectrolytes
Molecularcompounds tend tobe nonelectrolytes,except for acids andbases.
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AqueousReactions
2009, Prentice-Hall, Inc.
Electrolytes
A strong electrolyte dissociates completely
when dissolved inwater. A weak electrolyte
only dissociatespartially whendissolved in water.
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AqueousReactions
2009, Prentice-Hall, Inc.
Strong Electrolytes Are
Strong acids Strong bases
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AqueousReactions
2009, Prentice-Hall, Inc.
Strong Electrolytes Are
Strong acids Strong bases Soluble ionic salts
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AqueousReactions
2009, Prentice-Hall, Inc.
Precipitation Reactions
When one mixes ionsthat form compounds
that are insoluble (ascould be predicted bythe solubilityguidelines), a
precipitate is formed.
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AqueousReactions
2009, Prentice-Hall, Inc.
Metathesis (Exchange) Reactions
Metathesis comes from a Greek word thatmeans to transpose.
AgNO 3 ( aq ) + KCl (aq ) AgCl (s ) + KNO 3 ( aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Metathesis (Exchange) Reactions
Metathesis comes from a Greek word thatmeans to transpose.
It appears the ions in the reactantcompounds exchange, or transpose, ions.
Ag NO 3 ( aq ) + KCl (aq ) AgCl (s ) + KNO 3 ( aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Solution Chemistry
It is helpful to pay attention to exactly what species are present in a reaction
mixture (i.e., solid, liquid, gas, aqueoussolution).
If we are to understand reactivity, we
must be aware of just what is changingduring the course of a reaction.
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AqueousReactions
2009, Prentice-Hall, Inc.
Molecular Equation
The molecular equation lists the reactantsand products in their molecular form.
AgNO 3 (aq ) + KCl (aq ) AgCl (s ) + KNO 3 (aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Ionic Equation
In the ionic equation all strong electrolytes (strongacids, strong bases, and soluble ionic salts) aredissociated into their ions.
This more accurately reflects the species that arefound in the reaction mixture.
Ag+
(aq ) + NO 3-
(aq ) + K+
(aq ) + Cl-
(aq )
AgCl (s ) + K+ (aq ) + NO 3- (aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Net Ionic Equation
To form the net ionic equation, cross out anythingthat does not change from the left side of theequation to the right.
Ag +(aq) + NO 3-(aq ) + K +(aq) + Cl -(aq )
AgCl (s ) + K +(aq) + NO 3-(aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Net Ionic Equation
To form the net ionic equation, cross out anythingthat does not change from the left side of theequation to the right.
The only things left in the equation are those thingsthat change (i.e., react) during the course of thereaction.
Ag +(aq) + Cl -(aq ) AgCl (s )
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AqueousReactions
2009, Prentice-Hall, Inc.
Net Ionic Equation
To form the net ionic equation, cross out anythingthat does not change from the left side of theequation to the right.
The only things left in the equation are those thingsthat change (i.e., react) during the course of thereaction.
Those things that didnt change (and were deleted
from the net ionic equation) are called spectator ions .
Ag +(aq ) + NO 3-(aq ) + K +(aq ) + Cl -(aq )
AgCl (s ) + K +(aq ) + NO 3-(aq )
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AqueousReactions
2009, Prentice-Hall, Inc.
Writing Net Ionic Equations
1. Write a balanced molecular equation.2. Dissociate all strong electrolytes.3. Cross out anything that remains
unchanged from the left side to theright side of the equation.
4. Write the net ionic equation with thespecies that remain.
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AqueousReactions
2009, Prentice-Hall, Inc.
Acids
There are only sevenstrong acids:
Hydrochloric (HCl) Hydrobromic (HBr) Hydroiodic (HI) Nitric (HNO 3)
Sulfuric (H 2SO 4) Chloric (HClO 3) Perchloric (HClO 4)
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AqueousReactions
2009, Prentice-Hall, Inc.
Bases
Arrhenius defined basesas substances thatincrease theconcentration of OH when dissolved in water.
Brnsted and Lowrydefined them as proton
acceptors.
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AqueousReactions
2009, Prentice-Hall, Inc.
Bases
The strong basesare the soluble
metal salts ofhydroxide ion: Alkali metals Calcium
Strontium Barium
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AqueousReactions
2009, Prentice-Hall, Inc.
Acid-Base Reactions
In an acid-basereaction, the acid
donates a proton(H+) to the base.
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AqueousReactions
2009, Prentice-Hall, Inc.
Neutralization Reactions
Generally, when solutions of an acid and a base arecombined, the products are a salt and water.
CH3COOH (aq ) + NaOH (aq ) CH
3COONa (aq ) + H
2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Neutralization Reactions
When a strong acid reacts with a strong base, the netionic equation is
HCl (aq ) + NaOH (aq ) NaCl (aq ) + H2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Neutralization Reactions
When a strong acid reacts with a strong base, the netionic equation is
HCl (aq ) + NaOH (aq ) NaCl (aq ) + H2O (l )
H+ (aq ) + Cl - (aq ) + Na + (aq ) + OH -(aq ) Na + (aq ) + Cl - (aq ) + H 2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Neutralization Reactions
When a strong acid reacts with a strong base, the netionic equation is
HCl (aq ) + NaOH (aq ) NaCl (aq ) + H2O (l )
H+ (aq ) + Cl - (aq ) + Na + (aq ) + OH -(aq ) Na + (aq ) + Cl - (aq ) + H 2O (l )
H+ (aq ) + OH - (aq ) H2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Gas-Forming Reactions
Some metathesis reactions do not give theproduct expected.
In this reaction, the expected product (H 2CO 3)decomposes to give a gaseous product(CO 2).
CaCO3
(s ) + HCl (aq ) CaCl2
(aq ) + CO2
(g ) + H2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Gas-Forming Reactions
When a carbonate or bicarbonate reacts withan acid, the products are a salt, carbon
dioxide, and water.
CaCO 3 (s ) + HCl (aq ) CaCl 2 (aq ) + CO 2 (g ) + H 2O (l ) NaHCO 3 (aq ) + HBr (aq ) NaBr (aq ) + CO 2 (g ) + H 2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Gas-Forming Reactions
Similarly, when a sulfite reacts with an acid,the products are a salt, sulfur dioxide, and
water.
SrSO 3 (s ) + 2 HI (aq ) SrI 2 (aq ) + SO 2 (g ) + H 2O (l )
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AqueousReactions
2009, Prentice-Hall, Inc.
Gas-Forming Reactions
This reaction gives the predicted product, butyou had better carry it out in the hood, or you
will be very unpopular! But just as in the previous examples, a gas isformed as a product of this reaction.
Na 2S (aq ) + H 2SO 4 (aq ) Na 2SO 4 (aq ) + H 2S (g )
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation-Reduction Reactions
An oxidation occurswhen an atom or ion
loses electrons. A reduction occurswhen an atom or iongains electrons.
One cannot occurwithout the other.
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation Numbers
To determine if an oxidation-reductionreaction has occurred, we assign an
oxidation number to each element in aneutral compound or charged entity.
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation Numbers
Elements in their elemental form havean oxidation number of 0.
The oxidation number of a monatomicion is the same as its charge.
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation Numbers
Nonmetals tend to have negativeoxidation numbers, although some are
positive in certain compounds or ions.Oxygen has an oxidation number of 2,except in the peroxide ion in which it hasan oxidation number of 1.Hydrogen is 1 when bonded to a metal,+1 when bonded to a nonmetal.
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation Numbers
Nonmetals tend to have negativeoxidation numbers, although some are
positive in certain compounds or ions.Fluorine always has an oxidation numberof 1.
The other halogens have an oxidationnumber of 1 when they are negative; theycan have positive oxidation numbers,however, most notably in oxyanions.
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AqueousReactions
2009, Prentice-Hall, Inc.
Oxidation Numbers
The sum of the oxidation numbers in aneutral compound is 0.
The sum of the oxidation numbers in apolyatomic ion is the charge on the ion.
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AqueousReactions
2009, Prentice-Hall, Inc.
Displacement Reactions
In displacement reactions,ions oxidize an element.
The ions, then, arereduced.
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AqueousReactions
2009, Prentice-Hall, Inc.
Displacement Reactions
In this reaction,silver ions oxidizecopper metal.
Cu (s ) + 2 Ag + (aq ) Cu 2+ (aq ) + 2 Ag (s )
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AqueousReactions
2009, Prentice-Hall, Inc.
Displacement Reactions
The reverse reaction,however, does notoccur.
Cu 2+ (aq ) + 2 Ag (s ) Cu (s ) + 2 Ag + (aq ) x
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AqueousReactions
2009, Prentice-Hall, Inc.
Activity Series
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AqueousReactions
2009, Prentice-Hall, Inc.
Molarity
Two solutions can contain the samecompounds but be quite different because theproportions of those compounds are different.
Molarity is one way to measure theconcentration of a solution.
moles of solutevolume of solution in litersMolarity ( M ) =
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AqueousReactions
2009, Prentice-Hall, Inc.
Mixing a Solution
To create a solution of aknown molarity, oneweighs out a known mass(and, therefore, number ofmoles) of the solute.
The solute is added to avolumetric flask, and
solvent is added to the lineon the neck of the flask.
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AqueousReactions
2009, Prentice-Hall, Inc.
Dilution
One can also dilute a more concentratedsolution by Using a pipet to deliver a volume of the solution to
a new volumetric flask, and
Adding solvent to the line on the neck of the newflask.
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AqueousReactions
2009, Prentice-Hall, Inc.
Dilution
The molarity of the new solution can be determinedfrom the equation
M c V c = M d V d,
where M c and M d are the molarity of the concentrated and dilutesolutions, respectively, and V c and V d are the volumes of thetwo solutions.
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AqueousReactions
2009, Prentice-Hall, Inc.
Using Molarities inStoichiometric Calculations
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AqueousReactions
Titration
Titration is ananalyticaltechnique inwhich one cancalculate theconcentration
of a solute ina solution.