Download 36 Reactions 2

Chapter 3 & 4: Reactions Part 2
Read:
HW:
BLB 3.1–3.2; 4.2–4.4
BLB 4:19, 24, 39, 49a, c, e, f, 51b, d
Supplemental Reactions 3–5
• Combination reactions (Chapter 3)
2Mg(s) + O2(!) ! 2MgO(s)
• Decomposition reactions (Chapter 3)
Single Displacement Reactions
• Redox reactions
• Oxidation numbers
PbCO3(s) !PbO(s) + CO2(g)
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Page 1
• (Complete) Combustion reactions (Ch. 3.2)
C3H8(g) + 5O2 (g) ! 3CO2 (g) + 4H2O(g)
Know:
• Exchange reactions (Metathesis)
• Formation of a precipitate
• Formation of a gas
• Formation of a weak or non-electrolyte
(neutralization)
L. S. Van Der Sluys
Review Patterns of reactivity
Chapter 4 Reactions
• Exchange reactions (Chapter 4)
Precipitation
Pb(NO3)2(aq) + 2KI(aq) ! PbI(s) " + 2KNO3(aq)
Neutralization
NaOH(aq) + HCl(aq) ! NaCl(aq) + H2O(!)
Gas formation
2HCl(aq) + Na2S(aq) ! H2S(g) # + 2NaCl(aq)
• Single displacement reactions (Redox: Ch. 4)
2Ca(s) + O2(g) ! 2CaO(s)
L. S. Van Der Sluys
Page 2
Chapter 4 Reactions
Exchange Reactions: GAS FORMATION
1. direct production of a gas (EX: H2, NO2, SO2)
2. formation of a weak acid which decomposes to
a gas:
CO2
CO2
H 2S
Single Displacement reactions
(Oxidation-Reduction)
Oxidation of Calcium metal by molecular O2
N2
Example: Sodium Bicarbonate Plus HCl
Molecular Equation
What is the Chemical Reaction??
NaHCO3(aq)+HCl(aq) ! H2CO3(aq)+NaCl(aq)
"
Ionic Equation
Na (aq) + HCO3$ (aq) + H+(aq) + Cl$ (aq) !
H2CO3 (aq)+ Na+(aq)+Cl$ (aq)
"
+
Na (aq) + Cl$ (aq) + CO2(g)+ H2O(l)
+
Net Ionic Equation
L. S. Van Der Sluys
Page 3
Chapter 4 Reactions
!How do you know which species is
being oxidized and which is being
reduced??
L. S. Van Der Sluys
Page 4
Chapter 4 Reactions
Rules for determining Oxidation States
1. Oxidation state of atom in elemental form is zero.
e.g.
Cl2
O2
P4
C(s)
S8
2. The oxidation number of a monatomic ion equals its
charge.
3. Some elements have “common” oxidation numbers
that can be used as reference in determining the
oxidation numbers of other atoms in the compound.
Alkali metals
+1
Alkaline earth metals
+2
Fluorine
–1
Cl, Br, I
almost always
–1
O
usually –2
Oxidizing agents
species that is actually being reduced
(gaining e–) in reaction
examples of good oxidizing agents: O2,
halogens, H2O2, HNO3, Cr2O7–, MnO4–
peroxides (–1) & superoxides possible
H
usually
+1
Hydrides: metal-H compounds (–1)
4. Sum of oxidation numbers is equal to overall
charge of molecule or ion:
• For a neutral compound the sum of oxidation
numbers equals zero.
• For a polyatomic ion, the sum of the oxidation
numbers is equal to the charge on the ion.
5. Shared electrons are assigned to the more
electronegative atom of the pair:
The more electronegative atom will have a
negative oxidation number.
L. S. Van Der Sluys
Page 5
Chapter 4 Reactions
Reducing agents
species that is actually being oxidized
(losing e–) in reaction
examples of good reducing agents: H2,
C, metals
L. S. Van Der Sluys
Page 6
Chapter 4 Reactions
Oxidation-Reduction Reactions
Zn(s) + CuSO4(aq) ! ZnSO4(aq) +Cu(s)
Examples of Oxidation Reduction
Reactions
1. Acid + Metal
What is oxidized?
Mg(s) + 2HCl(aq) ! MgCl2 + H2(g)
What is reduced?
Ionic equation:
What is the oxidizing agent?
Net ionic equation:
Spectator Ions:
What is the reducing agent?
2. Salt + Metal
Fe(s) + Ni(NO3)2(aq) ! Fe(NO3)2 + Ni(s)
Ionic equation:
Ionic equation:
Net ionic equation:
Net ionic equation
Spectator Ions:
L. S. Van Der Sluys
Page 7
Chapter 4 Reactions
L. S. Van Der Sluys
Page 8
Chapter 4 Reactions
Activity Series
Using the Activity Series:
Predicts whether a certain metal will be
oxidized
Oxidation causes:
• destruction of the metal framework
• failure of machinery
• deterioration (think rust)
• weakening of metal
Will the metal element displace the atom from its
compound in a reaction?
Na(s) + H2O(l) !
Au(s) + H2O(g) !
Zn(s) + AgNO3(aq) !
Active metals
(groups IA, IIA, Al)
Inactive (inert metals): jewelry metals
Other metals are in between.
L. S. Van Der Sluys
Page 9
Chapter 4 Reactions
L. S. Van Der Sluys
Page 10
Chapter 4 Reactions
Remember: An element that is higher in the
activity series will displace an element below
it.
Zn(s) + CuSO4(aq) ! ZnSO4(aq)+ Cu(s)
Ag(s) + Cu(NO3)2(aq) ! NO REACTION
Demo:
Al(s) +
Al(s) +
L. S. Van Der Sluys
CuCl2(aq) !
HCl(aq) !
Page 11
AlCl3(aq)+ Cu(s)
AlCl3(aq)+ H2(g)
Chapter 4 Reactions
Practice Questions:
1. What is the oxidation state of Cu in
CuSO4?
2. What is the oxidation state of O in
CuSO4?
3. What is the oxidation state of S in
CuSO4?
L. S. Van Der Sluys
Page 12
Chapter 4 Reactions
Practice Question: What are the
spectator ions for the reaction provided
below? What is the net ionic reaction?
2HF
+ Ba(OH)2
! 2H2O
+ BaF2
Practice Question: What are the
spectator ions for the reaction provided
below? What is the net ionic reaction?
NH3
L. S. Van Der Sluys
+ HCl
! NH4+
Page 13
+ Cl
-
Chapter 4 Reactions