Unit 4 (Chapter 4):
Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Unit 4 (Chapter 4):
Aqueous Reactions & Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc.
Solutions:
+
• homogeneous mixtures: evenly mixed (same) • solvent is present in greatest abundance. • solute dissolved in/by solvent
Molarity • Molarity (M) is a measure of the concentration of a solution.
moles of solute (mol) Molarity (M) = liters of solution (L)
units:
mol/L
or
–1 · mol L
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 = 0.500 mol NaCl = 2.00 M NaCl 58.44 g NaCl 0.250 L
Solution Prep from Solid 1-Calc & Mass solute WS #1-2 2-Add solvent, swirl to dissolve Conc. Calc’s 3-Fill with DI water to mark 4-Mix (Cap & Invert to mix evenly)
WS Concentration & Dilutions #1 5.00 g NaHCO3 x
1 mol NaHCO3 x 1 L NaHCO3 = 84.01 g NaHCO3 0.100 mol NaHCO3 0.595 L NaHCO3
#2 159.62 g CuSO4 1.20 mol CuSO4 x 0.275 L CuSO4 x 1 L CuSO4 1 mol CuSO4
=
52.7 g CuSO4
Solution Prep by Dilution 1-Calc M1V1=M2V2 M1V1 = M2V2 2-Pipet V1 from concentrated WS #3-4 3-Fill to mark with DI water Dilutions 4-Mix (Cap & Invert to mix evenly)
WS Concentration & Dilutions M1V1 = M2V2 HW p.160 #60, 67 #3
M1V1 = M2V2 (12.0 M)V1 = (1.25 M)(500. mL) V1 = 52.1 mL (or 0.0521 L)
#4
M1V1 = M2V2 (2.50 M)V1 = (0.200 M)(250. mL) V1 = 20.0 mL (or 0.0200 L)
H
H H
–
O
O
Cl
+
H
Cl
H
H
HCl + H2O → H3O+ + Cl–
Acid: proton (H+) donor Base: proton (H+) acceptor
NH3 + H2O →
+ NH4 H
H H
N H
O
H H
H
N H
+
– OH
+ H
– O H
Strength of Acids and Bases STRONG: (complete ionization) (completely as ions) HA(aq) H+(aq) + A–(aq) MOH(aq)
M+(aq) + OH–(aq)
WEAK: (partial ionization) (mostly as molecules) HA(aq) + H2O(l) H3O+(aq) + A–(aq) B(aq) + H2O(l)
BH+(aq) + OH–(aq)
Only 6 strong acids: Strong Acids: • Nitric (HNO3) HI + H2O H3O+ + I– • Sulfuric (H SO ) 2 4 proton (H+) donors • Hydrochloric (HCl) • Hydrobromic (HBr) • Hydroiodic (HI) • Perchloric (HClO4)
The strong bases are Strong Bases: soluble hydroxides –) of… (OH – + OH + H3O H2O + H2O • Group 1 (Li,Na,K) + proton (H ) acceptors • CBS (Ca, Ba, Sr) Mg(OH)2 & Be(OH)2 are not soluble Hydroxides of Group I and CBS
ase
Salts: Ionic Solids: (metal-nonmetal) dissociate (dissolve) by separation into ions Electrolytes: ions in solution that conduct electricity
Non
Weak
C11H22O11 CH3OH H2O NO ions
only molecules
Strong
CH3COOH HNO2 NH3 SOME ions
NaOH HNO3 KCl ALL ions
partially completely HW ionize p.159 #33 dissociate
Electrolytes: Strong, Weak, or Non? (ions conduct electricity) metal-nonmetal
Compound
Ionic
HW p.157 #1,2,4,5,38 nonmetals (Covalent) Molecular
Acid (H____)
Not Acid
Weak STRONG Base KBr STRONG WEAK CaI2 NON (& NH3) (6) FeCl3 C11H22O11 NaOH HCl, HBr, HI CH3COOH C2H5OH HNO2 HNO3 Ca(OH)2 H2O HF (strong bases) H2SO4 HClO4
QUIZ!!! (at the bell) Electrolytes: Strong, Weak, or Non? metal-nonmetal
Compound
nonmetals (Covalent)
Ionic
STRONG
Molecular Acid (H____) STRONG (6)
Weak Base WEAK (& NH3)
Not Acid
NON
Acid-Base Neutralization Reactions strong acid (H+A–)
strong base (M+OH–)
ionic compound (M+A–)
ACID + BASE
SALT + WATER +
Cl
H
Na
O
water H 2O (HOH)
H
HCl(aq) + NaOH(aq)
Na
– Cl
H
O
H
NaCl(aq) + H2O(l)
HW p.159 #40a
Precipitation Reactions Double Replacement: 2 (aq) + (aq) 2
(precipitate) (aq) +
precipitate: insoluble product (as predicted by solubility rules)
Pb2+I–
( )
Solubility Rules ALWAYS Soluble ions: * Li+, Na+, K+, ... * NH4+ * NO3–
Group I (alkali metals) ammonium nitrate
Common Precipitates form with: Ag+, Pb2+, Hg2+ (AP/H) OH– (hydroxide) CO32– (carbonate)
WS Solubility & NIE’s #1
examples AgCl, PbI2 Cu(OH)2 CaCO3
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) • Cross out Spectator Ions (no change) (same state) (same charge) • only species left are those that react (change) during the course of the reaction.
Ag+(aq) + NO3–(aq) + K+(aq) + Cl–(aq) → Net NIE:
AgCl(s) + K+(aq) + NO3–(aq) Ag+(aq) + Cl–(aq) → AgCl(s)
Balanced Net Ionic Equations comp – diss – cross – net – bal 1. Write a Complete molecular equation. 2. Dissociate all strong electrolytes(aq) . 3. Cross out spectators (same charge & state)
(solubility rules)
4. Write the Net ionic equation with the species that remain. 5. Balance the NIE.
Balanced Net Ionic Equations comp – diss – cross – net – bal +
2–
2+
–
+
–
1) (NH4)2SO4 + Ba(NO3)2 → BaSO4 + NH4NO3
Ba2+ + SO42– → BaSO4 +
–
2+
–
+ –
2) NaOH + MgBr2 → NaBr + Mg(OH)2 Mg2+ + 2 OH– → Mg(OH)2(s) HW p.158 #21
Neutralization Reactions When a Strong Acid reacts with a Strong Base, the net ionic equation is…
H+ + OH– → H2O HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) H+ + Cl– + Na+ + OH– → Na+ + Cl– + H2O
Neutralization Reactions When a Weak acid reacts with a Strong base, the net ionic equation is…
HX + OH– → X– + H2O HF(aq) + KOH(aq) → KF(aq) + H2O(l) (dissociate ONLY STRONG electrolytes)
HF + K+ + OH– → K+ + F– + H2O HW p.159 #40 (finish)
Balanced Net Ionic Equations comp – diss – cross – net – bal +
2–
2+
–
+
–
(NH4)2SO4 + Ba(NO3)2 → BaSO4 + NH4NO3
Ba2+ + SO42– → BaSO4(s) +
–
+ –
HF(aq) + KOH(aq) → KF(aq) + H2O(l) HF + OH– → F– + H2O WS Solubility & NIE’s #2
Gas-Forming Reactions H2 Demo
(M0) (H+) Single Rep: Metal + Acid + 2–
Ex: Zn(s) + H2SO4(aq) NIE: Zn(s) + 2 H+(aq)
(M+) (gas) Metal Ion + H2 2+ 2–
ZnSO4(aq) + H2(g) Zn2+(aq) + H2(g)
(gas) H2O(l) + CO2(g) (CO32–) CO2 Demo (H+) Double Rep: Acid + Carbonate Salt + H2CO3(aq) (or Bicarbonate) (decomposes HW p. 159 #43 (HCO3–) immediately) Ex: HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) + CO2(g) NIE: 2 H+(aq) + CaCO3(s) Ca2+(aq) + H2O(l) + CO2(g) CH3COOH + NaHCO3 CH3COONa + H2O + CO2
Solution Stoichiometry Rxn: gA
A(aq) + 2 B(aq) C + 2 D molar mass A g A 1 mol A
mol A
L of A
mol A 1L
mol-to-mol ratio
gB
molarity A (M)
HW p. 161 #81
g B 1 mol B
mol B 1L
molar mass B
molarity B (M)
mol B
L of B
Oxidation-Reduction Reactions (REDOX)
video clip
(One cannot occur without the 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) *charges of ions show electrons transferred IN an ionic compound
*oxidation numbers of elements describe electrons that would be lost or gained IF the compound was 100% ionic.
in Na2O, O2– in H2O, O–2
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, but some are positive in certain compounds or ions. (in SO3 , O is –2 but S is +6)
O is −2 always but in peroxide ion is −1 (O22–) H is +1 with nonmetals, −1 with metals F is always −1. other halogens are −1, BUT can be positive, like in oxyanions. Ex. ClO3– or NO3– or SO42–
Oxidation Numbers • The sum of the ox. #’s in a neutral compound 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) Synthesis A + B → AB (0 0 → +/–)
Decomposition 2→1
AB → A + B (+/– → 0 0)
1→2
Single Replacement
Combustion
AB + C → A + CB (+/– 0 → 0 +/–)
CxHy + O2 → CO2 + H2O (–/+ 0 → +/– +/–)
Single Replacement (REDOX)
silver ions oxidize copper metal
Cu(s) + 2 Ag+(aq) → Cu2+(aq) + 2 Ag(s) +(aq) Cu2+(aq) + 2 Ag(s) → Cu (s) + 2 Ag X
Cannot displace H+ from acid to make H2(g)
increasing ease of oxidation
Activity Series of Metals
Writing REDOX Reactions Write the net ionic equation for the reaction of solid zinc in a solution of hydrochloric acid.
comp – diss – cross – net – bal 0
+1 –1
+2 –1
0
Mg(s) + HCl(aq) MgCl2(aq) + H2(g) Mg + 2 H+ Mg+2 + H2 Classify the reaction in two ways. Single-Replacement and Redox
ox
Mg + 2 H+ Mg2+ + H2(g) red What is red & what is ox? WS Aq Soln’s & Chem Rxns
Unit 4 (Chapter 4):
Aqueous Reactions & Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc.
Solutions:
+
• homogeneous mixtures: evenly mixed (same) • solvent is present in greatest abundance. • solute dissolved in/by solvent
Molarity • Molarity (M) is a measure of the concentration of a solution.
moles of solute (mol) Molarity (M) = liters of solution (L)
units:
mol/L
or
–1 · mol L
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 = 0.500 mol NaCl = 2.00 M NaCl 58.44 g NaCl 0.250 L
Solution Prep from Solid 1-Calc & Mass solute WS #1-2 2-Add solvent, swirl to dissolve Conc. Calc’s 3-Fill with DI water to mark 4-Mix (Cap & Invert to mix evenly)
WS Concentration & Dilutions #1 5.00 g NaHCO3 x
1 mol NaHCO3 x 1 L NaHCO3 = 84.01 g NaHCO3 0.100 mol NaHCO3 0.595 L NaHCO3
#2 159.62 g CuSO4 1.20 mol CuSO4 x 0.275 L CuSO4 x 1 L CuSO4 1 mol CuSO4
=
52.7 g CuSO4
Solution Prep by Dilution 1-Calc M1V1=M2V2 M1V1 = M2V2 2-Pipet V1 from concentrated WS #3-4 3-Fill to mark with DI water Dilutions 4-Mix (Cap & Invert to mix evenly)
WS Concentration & Dilutions M1V1 = M2V2 HW p.160 #60, 67 #3
M1V1 = M2V2 (12.0 M)V1 = (1.25 M)(500. mL) V1 = 52.1 mL (or 0.0521 L)
#4
M1V1 = M2V2 (2.50 M)V1 = (0.200 M)(250. mL) V1 = 20.0 mL (or 0.0200 L)
H
H H
–
O
O
Cl
+
H
Cl
H
H
HCl + H2O → H3O+ + Cl–
Acid: proton (H+) donor Base: proton (H+) acceptor
NH3 + H2O →
+ NH4 H
H H
N H
O
H H
H
N H
+
– OH
+ H
– O H
Strength of Acids and Bases STRONG: (complete ionization) (completely as ions) HA(aq) H+(aq) + A–(aq) MOH(aq)
M+(aq) + OH–(aq)
WEAK: (partial ionization) (mostly as molecules) HA(aq) + H2O(l) H3O+(aq) + A–(aq) B(aq) + H2O(l)
BH+(aq) + OH–(aq)
Only 6 strong acids: Strong Acids: • Nitric (HNO3) HI + H2O H3O+ + I– • Sulfuric (H SO ) 2 4 proton (H+) donors • Hydrochloric (HCl) • Hydrobromic (HBr) • Hydroiodic (HI) • Perchloric (HClO4)
The strong bases are Strong Bases: soluble hydroxides –) of… (OH – + OH + H3O H2O + H2O • Group 1 (Li,Na,K) + proton (H ) acceptors • CBS (Ca, Ba, Sr) Mg(OH)2 & Be(OH)2 are not soluble Hydroxides of Group I and CBS
ase
Salts: Ionic Solids: (metal-nonmetal) dissociate (dissolve) by separation into ions Electrolytes: ions in solution that conduct electricity
Non
Weak
C11H22O11 CH3OH H2O NO ions
only molecules
Strong
CH3COOH HNO2 NH3 SOME ions
NaOH HNO3 KCl ALL ions
partially completely HW ionize p.159 #33 dissociate
Electrolytes: Strong, Weak, or Non? (ions conduct electricity) metal-nonmetal
Compound
Ionic
HW p.157 #1,2,4,5,38 nonmetals (Covalent) Molecular
Acid (H____)
Not Acid
Weak STRONG Base KBr STRONG WEAK CaI2 NON (& NH3) (6) FeCl3 C11H22O11 NaOH HCl, HBr, HI CH3COOH C2H5OH HNO2 HNO3 Ca(OH)2 H2O HF (strong bases) H2SO4 HClO4
QUIZ!!! (at the bell) Electrolytes: Strong, Weak, or Non? metal-nonmetal
Compound
nonmetals (Covalent)
Ionic
STRONG
Molecular Acid (H____) STRONG (6)
Weak Base WEAK (& NH3)
Not Acid
NON
Acid-Base Neutralization Reactions strong acid (H+A–)
strong base (M+OH–)
ionic compound (M+A–)
ACID + BASE
SALT + WATER +
Cl
H
Na
O
water H 2O (HOH)
H
HCl(aq) + NaOH(aq)
Na
– Cl
H
O
H
NaCl(aq) + H2O(l)
HW p.159 #40a
Precipitation Reactions Double Replacement: 2 (aq) + (aq) 2
(precipitate) (aq) +
precipitate: insoluble product (as predicted by solubility rules)
Pb2+I–
( )
Solubility Rules ALWAYS Soluble ions: * Li+, Na+, K+, ... * NH4+ * NO3–
Group I (alkali metals) ammonium nitrate
Common Precipitates form with: Ag+, Pb2+, Hg2+ (AP/H) OH– (hydroxide) CO32– (carbonate)
WS Solubility & NIE’s #1
examples AgCl, PbI2 Cu(OH)2 CaCO3
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) • Cross out Spectator Ions (no change) (same state) (same charge) • only species left are those that react (change) during the course of the reaction.
Ag+(aq) + NO3–(aq) + K+(aq) + Cl–(aq) → Net NIE:
AgCl(s) + K+(aq) + NO3–(aq) Ag+(aq) + Cl–(aq) → AgCl(s)
Balanced Net Ionic Equations comp – diss – cross – net – bal 1. Write a Complete molecular equation. 2. Dissociate all strong electrolytes(aq) . 3. Cross out spectators (same charge & state)
(solubility rules)
4. Write the Net ionic equation with the species that remain. 5. Balance the NIE.
Balanced Net Ionic Equations comp – diss – cross – net – bal +
2–
2+
–
+
–
1) (NH4)2SO4 + Ba(NO3)2 → BaSO4 + NH4NO3
Ba2+ + SO42– → BaSO4 +
–
2+
–
+ –
2) NaOH + MgBr2 → NaBr + Mg(OH)2 Mg2+ + 2 OH– → Mg(OH)2(s) HW p.158 #21
Neutralization Reactions When a Strong Acid reacts with a Strong Base, the net ionic equation is…
H+ + OH– → H2O HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) H+ + Cl– + Na+ + OH– → Na+ + Cl– + H2O
Neutralization Reactions When a Weak acid reacts with a Strong base, the net ionic equation is…
HX + OH– → X– + H2O HF(aq) + KOH(aq) → KF(aq) + H2O(l) (dissociate ONLY STRONG electrolytes)
HF + K+ + OH– → K+ + F– + H2O HW p.159 #40 (finish)
Balanced Net Ionic Equations comp – diss – cross – net – bal +
2–
2+
–
+
–
(NH4)2SO4 + Ba(NO3)2 → BaSO4 + NH4NO3
Ba2+ + SO42– → BaSO4(s) +
–
+ –
HF(aq) + KOH(aq) → KF(aq) + H2O(l) HF + OH– → F– + H2O WS Solubility & NIE’s #2
Gas-Forming Reactions H2 Demo
(M0) (H+) Single Rep: Metal + Acid + 2–
Ex: Zn(s) + H2SO4(aq) NIE: Zn(s) + 2 H+(aq)
(M+) (gas) Metal Ion + H2 2+ 2–
ZnSO4(aq) + H2(g) Zn2+(aq) + H2(g)
(gas) H2O(l) + CO2(g) (CO32–) CO2 Demo (H+) Double Rep: Acid + Carbonate Salt + H2CO3(aq) (or Bicarbonate) (decomposes HW p. 159 #43 (HCO3–) immediately) Ex: HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) + CO2(g) NIE: 2 H+(aq) + CaCO3(s) Ca2+(aq) + H2O(l) + CO2(g) CH3COOH + NaHCO3 CH3COONa + H2O + CO2
Solution Stoichiometry Rxn: gA
A(aq) + 2 B(aq) C + 2 D molar mass A g A 1 mol A
mol A
L of A
mol A 1L
mol-to-mol ratio
gB
molarity A (M)
HW p. 161 #81
g B 1 mol B
mol B 1L
molar mass B
molarity B (M)
mol B
L of B
Oxidation-Reduction Reactions (REDOX)
video clip
(One cannot occur without the 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) *charges of ions show electrons transferred IN an ionic compound
*oxidation numbers of elements describe electrons that would be lost or gained IF the compound was 100% ionic.
in Na2O, O2– in H2O, O–2
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, but some are positive in certain compounds or ions. (in SO3 , O is –2 but S is +6)
O is −2 always but in peroxide ion is −1 (O22–) H is +1 with nonmetals, −1 with metals F is always −1. other halogens are −1, BUT can be positive, like in oxyanions. Ex. ClO3– or NO3– or SO42–
Oxidation Numbers • The sum of the ox. #’s in a neutral compound 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) Synthesis A + B → AB (0 0 → +/–)
Decomposition 2→1
AB → A + B (+/– → 0 0)
1→2
Single Replacement
Combustion
AB + C → A + CB (+/– 0 → 0 +/–)
CxHy + O2 → CO2 + H2O (–/+ 0 → +/– +/–)
Single Replacement (REDOX)
silver ions oxidize copper metal
Cu(s) + 2 Ag+(aq) → Cu2+(aq) + 2 Ag(s) +(aq) Cu2+(aq) + 2 Ag(s) → Cu (s) + 2 Ag X
Cannot displace H+ from acid to make H2(g)
increasing ease of oxidation
Activity Series of Metals
Writing REDOX Reactions Write the net ionic equation for the reaction of solid zinc in a solution of hydrochloric acid.
comp – diss – cross – net – bal 0
+1 –1
+2 –1
0
Mg(s) + HCl(aq) MgCl2(aq) + H2(g) Mg + 2 H+ Mg+2 + H2 Classify the reaction in two ways. Single-Replacement and Redox
ox
Mg + 2 H+ Mg2+ + H2(g) red What is red & what is ox? WS Aq Soln’s & Chem Rxns
