Unit 4 (Chapter 4): Aqueous Reactions & Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
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Unit 4 (Chapter 4):
Aqueous Reactions &
Solution Stoichiometry
John D. Bookstaver
St. Charles Community College
St. Peters, MO
2006, Prentice Hall, Inc.
Chemistry, The Central Science, 10th editionTheodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Solutions:
• homogeneous mixtures:
evenly mixed (same)
• solvent is present in greatest abundance.
• solute dissolvedin/by solvent
+
0.250 L
Molarity
• Molarity (M) is a measure of the concentration of a solution.
moles of solute (mol)
liters of solution (L)Molarity (M) =
units: mol/L or mol·L–1
What’s the concentration of a solution with 29.2 g of sodium chloride in 250. mL of water?
29.2 g NaCl x 1 mol NaCl
58.44 g NaCl= 0.500 mol NaCl = 2.00 M
NaCl
Solution Prep from Solid1-Calc & Mass solute
2-Add solvent, swirl to dissolve
3-Fill with DI water to mark
4-Mix (Cap & Invert to mix evenly)
WS #1-2
Conc.
Calc’s
WS Concentration & Dilutions
0.100 mol NaHCO3
5.00 g NaHCO3 x 1 mol NaHCO3
84.01 g NaHCO3
x 1 L NaHCO3 =
0.595 L
NaHCO3
#1
1 mol CuSO4
0.275 L CuSO4 x 1.20 mol CuSO4
1 L CuSO4
x 159.62 g CuSO4 =
52.7 g
CuSO4
#2
1-Calc M1V1=M2V2
2-Pipet V1 from concentrated
3-Fill to mark with DI water
4-Mix (Cap & Invert to mix evenly)
M1V1 = M2V2
Solution Prep by Dilution
WS #3-4
Dilutions
WS Concentration & Dilutions
#3
#4
M1V1 = M2V2
M1V1 = M2V2
(12.0 M)V1 = (1.25 M)(500. mL)
V1 = 52.1 mL (or 0.0521 L)
M1V1 = M2V2
(2.50 M)V1 = (0.200 M)(250. mL)
V1 = 20.0 mL (or 0.0200 L)
HW p.160 #60, 67
HCl + H2O → H3O+ + Cl–
H
H H
H
HHO OCl Cl
+ –
NH3 + H2O → NH4+ + OH–
H
H
H
H
H
H
HH
H H
N O ON
+ –
�Acid: proton (H+) donor
�Base: proton (H+) acceptor
Strength of Acids and Bases
(complete ionization) (completely as ions)
HA(aq) H+(aq) + A–(aq)
MOH(aq) M+(aq) + OH–(aq)
(partial ionization) (mostly as molecules)
HA(aq) + H2O(l) H3O+(aq) + A–(aq)
B(aq) + H2O(l) BH+(aq) + OH–(aq)
STRONG:
WEAK:
Strong Acids: Only 6 strong acids:
• Nitric (HNO3)
• Sulfuric (H2SO4)
• Hydrochloric (HCl)
• Hydrobromic (HBr)
• Hydroiodic (HI)
• Perchloric (HClO4)
proton (H+) donors
HI + H2O � H3O+ + I–
Strong Bases:The strong bases are soluble hydroxides
(OH–) of…
• Group 1 (Li,Na,K)
• CBS (Ca, Ba, Sr)
Mg(OH)2 & Be(OH)2
are not soluble
proton (H+) acceptors
OH– + H3O+ � H2O + H2O
aseHydroxides of
Group I
and CBS
Salts:Ionic Solids: (metal-nonmetal)dissociate (dissolve) by separation into ions
Electrolytes:ions in solution that conduct electricity
StrongWeak
C11H22O11
CH3OH
H2O
Non
CH3COOH
HNO2
NH3
NaOH
HNO3
KCl
completely
dissociate
partially
ionize
only
molecules
NOions
ALLions
SOMEions
HW
p.159 #33
Electrolytes: Strong, Weak, or Non?
Compound
Ionic
STRONG
Molecular
Acid
(H____)
STRONG
(6)
WEAK
Not Acid
NON
HW p.157 #1,2,4,5,38
nonmetals (Covalent)metal-nonmetal
C11H22O11
C2H5OH
H2O
CH3COOH
HNO2
HF
KBr
CaI2FeCl3NaOH
Ca(OH)2
(strong bases)
HCl, HBr, HI
HNO3
H2SO4
HClO4
(ions conduct electricity)
Weak
Base
(& NH3)
Electrolytes: Strong, Weak, or Non?Compound
Ionic
STRONG
Molecular
Acid
(H____)
WEAK
Not Acid
NON
nonmetals (Covalent)metal-nonmetal
STRONG
(6)
QUIZ!!!(at the bell)
Weak
Base
(& NH3)
ClNaHONa
strong acid
(H+A–)
strong base
(M+OH–)
HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
ACID + BASE SALT + WATER
H HHOCl
+ –
ioniccompound
(M+A–)
waterH2O
(HOH)
Acid-Base Neutralization Reactions
HW p.159 #40a
2 (aq) + (aq) ���� 2 (aq) + ( )
Double Replacement: (precipitate)
precipitate:insoluble product(as predicted by solubility rules)
Precipitation Reactions
Pb2+
I–
ALWAYS Soluble ions:
Li+, Na+, K+, ... Group I (alkali metals)
NH4+ ammonium
NO3– nitrate
Solubility Rules
Common Precipitates form with: examples
Ag+, Pb2+, Hg2+ (AP/H) AgCl, PbI2OH– (hydroxide) Cu(OH)2
CO32– (carbonate) CaCO3
*
*
*
WS Solubility & NIE’s #1
Molecular Equation• reactants and products in molecular form
AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq)
Ionic Equation
• Strong Electrolytes are Dissociated as ions (strong acids, strong bases, soluble salts)
Ag+(aq) + NO3
–(aq) + K+
(aq) + Cl–(aq) →
AgCl(s) + K+(aq) + NO3
–(aq)
Net Ionic Equation (NIE)
Ag+(aq) + NO3
–(aq) + K+
(aq) + Cl–(aq) →
AgCl(s) + K+(aq) + NO3
–(aq)
NIE: Ag+(aq) + Cl–(aq) → AgCl(s)
• Cross out Spectator Ions (no change)
• only species left are those that react(change) during the course of the reaction.
Net
(same state)(same charge)
Balanced Net Ionic Equations
1. Write a Complete molecular equation.
2. Dissociate all strong electrolytes(aq) .
3. Cross out spectators(same charge & state)
4. Write the Net ionic equation with the species that remain.
5. Balance the NIE.
comp – diss – cross – net – bal
(solubility rules)
BaSO4 + NH4NO3
Balanced Net Ionic Equations
1) (NH4)2SO4 + Ba(NO3)2 →
2) NaOH + MgBr2 →
comp – diss – cross – net – bal
+ 2– 2+ –– +
Ba2+ + SO42– → BaSO4
NaBr + Mg(OH)2
+ – 2+ –– +
Mg2+ + 2 OH– → Mg(OH)2(s)
HW p.158 #21
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
H+ + Cl– + Na+ + OH–→ Na+ + Cl– + H2O
Neutralization Reactions
H+ + OH–→→→→ H2O
When a Strong Acid reacts with a Strong Base,
the net ionic equation is…
HF(aq) + KOH(aq) → KF(aq) + H2O(l)
HF + K+ + OH–→ K+ + F– + H2O
Neutralization Reactions
HX + OH–→→→→ X– + H2O
HW p.159 #40 (finish)
When a Weak acid reacts with a Strong base,
the net ionic equation is…
(dissociate ONLY
STRONG electrolytes)
BaSO4 + NH4NO3
Balanced Net Ionic Equations
(NH4)2SO4 + Ba(NO3)2 →
comp – diss – cross – net – bal
+ 2– 2+ –– +
Ba2+ + SO42– → BaSO4(s)
HF(aq) + KOH(aq) → KF(aq) + H2O(l)
WS Solubility & NIE’s #2
HF + OH–→ F– + H2O
–+–+
Gas-Forming Reactions
Single Rep: Metal + Acid Metal Ion + H2
Ex: Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)
NIE: Zn(s) + 2 H+(aq) Zn2+(aq) + H2(g)
H2 Demo (M0) (H+) (M+) (gas)
+ 2– 2+ 2–
Double Rep: Acid + Carbonate Salt +
Ex: HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) + CO2(g)
NIE: 2 H+(aq) + CaCO3(s) Ca2+(aq) + H2O(l) + CO2(g)
(or Bicarbonate)
(HCO3–)
(CO32–)(H+)
CH3COOH + NaHCO3 � CH3COONa + H2O + CO2
HW p. 159 #43
H2CO3(aq)
H2O(l) + CO2(g)
(decomposes
immediately)
(gas)
CO2 Demo
g A L of A
g B mol B L of B
g A
1 mol Amol A
1 L
g B
1 mol B
mol B
1 L
molar
mass A
molar
mass B
molarity
A (M)
molarity
B (M)
mol-to-mol ratio
mol A
Rxn: A(aq) + 2 B(aq) ���� C + 2 D
Solution Stoichiometry
HW p. 161 #81
Oxidation-Reduction Reactions
(REDOX)video clip
(Onecannotoccur withoutthe other)
LEO says
GER
Oxidation Numbers
Is it a redox reaction? To find out…
1) assign oxidation numbers* (or oxidation states)
to each element in a reaction.
2) check if any oxidation states changed
(↓ reduced , ↑ oxidized)
of elements describe
electrons that would be lost or gained IF
the compound was 100% ionic.
*oxidation numbers
*charges
in H2O,
O–2
of ions show electrons
transferred IN an ionic compound
in Na2O,
O2–
� F is always −1.
� other halogens are −1, BUT can be positive, like in oxyanions.
Ex. ClO3– or NO3
– or SO42–
Assigning Oxidation Numbers
1. All pure elements are 0
2. Monatomic ion is its charge (Mg2+ has +2)
3. Most nonmetals tend to be negative, butsome are positive in certain compounds or ions.� O is −2 always
� H is +1 with nonmetals, −1 with metals
O is –2 but S is +6)(in SO3 ,but in peroxide ion is −1 (O2
2–)
Oxidation Numbers
• The sum of the ox. #’s in a neutralcompound is 0.
• The sum of the ox. #’s in a polyatomic ion is the charge on the ion.
Determine the oxidation number of:
Sulfur in… SO2
Chromium in… K2Cr2O7
Nitrogen in… NH4+
Cobalt in… [CoCl6]3–
Classifying REDOX Reactions
All rxns (but…NOT double replacement)
Decomposition
AB → A + B 1 → 2
(+/– → 0 0)
CombustionCxHy + O2 → CO2 + H2O
(–/+ 0 → +/– +/–)
Single ReplacementAB + C → A + CB
(+/– 0 → 0 +/–)
Synthesis
A + B → AB 2 → 1
(0 0 → +/–)
Single Replacement (REDOX)
Cu2+(aq) + 2 Ag(s) → Cu(s) + 2 Ag+(aq)X
Cu(s) + 2 Ag+(aq) → Cu2+(aq) + 2 Ag(s)
silver ions
oxidize
copper metal
Activity
Series
of
Metals
incre
asin
g e
ase
of
oxid
atio
n
Cannotdisplace H+
from acid to
make H2(g)
Write the net ionic equation for the reaction of solid zinc in a solution of hydrochloric acid.
Writing REDOX Reactions
Mg(s) + HCl(aq) ���� MgCl2(aq) + H2(g)
comp – diss – cross – net – bal
0 +1 –1 +2 –1 0
Mg + H+ ���� Mg+2 + H22
Classify the reaction in two ways.
Single-Replacement and Redox
Mg + 2 H+ � Mg2+ + H2(g)
WS Aq Soln’s& Chem Rxns
What is red & what is ox?red
ox
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