5 - 1ch110: ch110 chapter 7 chemical reactions chemical equations types of reactions...
TRANSCRIPT
5 - 1CH110:
CH110 Chapter 7Chemical Reactions
Chemical Equations
Types of Reactions
Oxidation-Reduction
Energy in Chemical Reactions
Reaction Rates
Omit: Moles (7.1; 7.2; 7.6; 7.7)
5 - 2CH110:
What is Chemistry?“The study of Matter and its Changes.”
Physical Changes =
Changes in a Physical Property
Chemical Changes =
Changes in a Chemical Property
Appearance: • melting, freezing, evaporation…• stretching, molding, cutting…
Chemical Composition:
5 - 3CH110:
Change in the Chemical Composition
Burning of Magnesium
Chemical Changes
Rusting of Iron
Decomposing of wood
Souring of Milk
Examples:
5 - 4CH110:
Chemical Reactions
• Color change
• Gas formed
• Solid precipitate formed
• Temperature Change
• Gives heat = exothermic
• Gets cold = endothermic
5 - 5CH110:
Mg + O2 MgO +
Energy
Chemical Reactions
Shows how the Chemical change occurs.Shows how the Chemical change occurs.
Reactants
C3H8 + O2 CO2 + H2O + Energy
Fe + O2 Fe2O3
ProductsProducts
5 - 6CH110:
Chemical equations
Chemist’s shorthand to describe a reaction.
•Reactants •Products
•The state of all substances
H2 + O2 H2O + E(g) (g) (g)
•Any conditions used in the reaction
heat
•Same # & type atoms on each side• Law of Conservation of Matter
2 2
(g) (l) (s) (aq)(g) (l) (s) (aq)
5 - 7CH110:
Balancing Equations
___W10 + ___B8 ___WB___W10 + ___B8 ___WB
•Reactants •Products
Making Hot dogs:How many packages wieners & buns to buy so none is left over.
4 5 40
5 - 11CH110:
NaPO
MgCl
Balancing Equations
Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl
•Reactants •Products
Step 1: Count atoms of each element on both sides of equation.
31412
1 2831
5 - 12CH110:
NaPO
MgCl
Balancing Equations
Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl
•Reactants •Products31412
1 2831
- not balanced
- not balanced
Step 2: Determine which atoms are not balanced.
- not balanced
- not balanced
- not balanced
5 - 13CH110:
NaPO
MgCl
Balancing Equations
Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl
•Reactants •Products31412
1 2831
- not balanced
- not balanced
- not balanced
- not balanced
- not balanced
Step 3: Balance elements with #’s in front of formulas until all balanced.
(Never change the formulas!)
5 - 14CH110:
Hints:• Start with a metal in a complex
compound, or an element that only appears in one formula. (ie Mg here)
NaPO
MgCl
Balancing Equations
Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl Na3PO4 + MgCl2 Mg3(PO4)2 + NaCl
•Reactants •Products31412
1 2831
- not balanced
- not balanced
- not balanced
- not balanced
- not balanced66
66
63
33
22
66
1
88
2
66
5 - 15CH110:
Hints:• Start with an element that only appears
in one formula on both sides of the equation.
• Leave oxygen until last.
Balancing Equations
C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
•Reactants •ProductsC
H
O
5 - 16CH110:
Balancing Equations
C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
C
H
O
C
H
O
•Reactants •Products
Step 1: Count atoms of each element on both sides of equation.
2
6
2
2
6
2
1
2
3
1
2
3
5 - 17CH110:
C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
Balancing Equations
•Reactants •Products
2
6
2
2
6
2
1
2
3
1
2
3
Step 2: Determine which atoms are not balanced.
- not balanced
- not balanced
- not balancedC
H
O
C
H
O
5 - 18CH110:
2
6
2
2
6
2
- not balanced
- not balanced
C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
22
Balancing Equations
•Reactants •Products
1
2
3
1
2
3
- not balanced
Step 3: Balance one element at a time with coefficients in front of formulas until all balanced.
(Never change the formula!)
2
55
3
66
77
3.5
77
C
H
O
C
H
O
5 - 19CH110:
C
H
O
C
H
O
C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
22
Balancing Equations
•Reactants •Products
2
6
2
2
6
2
1
2
3
1
2
3
2
55
3
66
77
3.5
77
Can’t have 3.5 O2 , so multiply equation by 2!
5 - 20CH110:
3.5C2H6 + O2 CO2 + H2OC2H6 + O2 CO2 + H2O
22
Balancing Equations
C
H
O
C
H
O
•Reactants •Products
2
6
2
2
6
2
1
2
3
1
2
3
4
55
6
66
77
7
77
Can’t have 3.5 O2 , so multiply equation by 2!
2
44 44
1212 1212
1414 1414
5 - 21CH110:
Types of Chemical Reactions
Complete:C3H8 + 5O2 3CO2 + 4H2O
Combustion
Incomplete:2C3H8 + 7O2 6CO + 8H2O
C3H8 + 2O2 3C + 4H2O
5 - 22CH110:
Types of Chemical Reactions
Combination
Decomposition
Single Replacement: Substitution
Double Replacement: Metathesis
A + BX B + AX
A + B C
C A + B
AX + BY BX + AY
5 - 23CH110:
Combination Reactions
Rusting of Iron
4 Fe + 3 O2 2 Fe2O3
Formation of Acid Rain
SO3 + H2O H2SO4
2H2 + O2 2H2O
Exposion of Hydrogen Balloon
A + B C A + B C
Types of Chemical Reactions
5 - 24CH110:
Decomposition Reactions
Heating Egg Shells
CaCO3 CaO + CO2
2 H2O2 2 H2O + O2
Blood with peroxide
C A + B
Types of Chemical Reactions
5 - 25CH110:
Single Replacement Reactions
Iron Deposits on an Aluminum Pan
Al + FeCl3 Fe + AlCl3
A + BX B + AX
Types of Chemical Reactions
5 - 26CH110:
Activity series of metalspotassiumsodium
potassiumsodium
calciumcalcium
magnesiumaluminum
zincchromium
magnesiumaluminum
zincchromium
ironnickel
tinlead
ironnickel
tinlead
coppersilver
platinumgold
coppersilver
platinumgold
Hydrogen
Al + Fe+3 Fe + Al+3
Fe + H+ Fe+3 + H2
incr
easi
ng
rea
ctiv
ity
Element give e’s to ion
lower on list
Element give e’s to ion
lower on list
5 - 27CH110:
Double Replacement Reaction
BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)
AX + BY BX + AY AX + BY BX + AY
Ba+2 Cl-1
Na+1 SO4-2
Insoluble PrecipitateFormed
Types of Chemical Reactions
5 - 28CH110:
Predict the products:
AgNO3(aq) + MgCl2(aq)
Ag+ NO3
-
Mg+2 Cl-
AgCl(s)
Double Replacement ReactionAX + BY BX + AY AX + BY BX + AY
Write correct formulas then balance as needed
2 2 + Mg(NO3)2(aq)
5 - 29CH110:
Oxidation and reductionREDOX
Where reactants exchange electrons -
Examples:
•All types of batteries
alkaline, NiCad, car batteries•Rusting and corrosion•Metabolism•Antioxidants (Vit C, E prevent oxidation)
5 - 30CH110:
Oxidation and ReductionREDOXWhere reactants exchange electrons -
LEO the lion says GER LEO the lion says GER
Reduction = Gaining electrons GER: Gain Electrons Reduction
Oxidation = Losing electronsLEO: Lose Electrons Oxidation
5 - 31CH110:
Oxidation and ReductionReduction =
GERGain e-s so gets more -
Oxidation = LEO
Lose e-s so gets more +
0+1+2+3+4
-1-2-3
-4
Fe3+ Fe2+
Na Na1+
5 - 32CH110:
Oxidation and Reduction
2 Na(s) + Cl2 (g) 2 NaCl2 Na(s) + Cl2 (g) 2 NaCl
1-1+
1. Assign Oxidation States:
0 0For simple ions,
Ox state = charge.
For element in natural form
Ox State = 0.
5 - 33CH110:
Oxidation and Reduction
2 Na(s) + Cl2 (g) 2 NaCl2 Na(s) + Cl2 (g) 2 NaCl
1-1+
2. Who’s loosing or gaining electrons?
0 0
Loses 1 e- = LEO
Gains 1 e-=GER
Na loses e- (LEO) Na gets oxidized
Cl gains e- (GER) Cl gets reduced
5 - 35CH110:
Oxidation and Reduction
2 Na(s) + Cl2 (g) 2 NaCl2 Na(s) + Cl2 (g) 2 NaCl
1-1+
Who’s loosing or gaining electrons?
0 0
• Na loses e- (LEO) so Na gets oxidized
• Na caused Cl to get reduced• Na is the Reducing agent
Loses 1 e- =LEO
Gains 1 e- =GER
5 - 36CH110:
Oxidation and Reduction
2 Na(s) + Cl2 (g) 2 NaCl2 Na(s) + Cl2 (g) 2 NaCl
1-1+
Who’s loosing or gaining electrons?
0 0
Loses 1 e- =LEO
Gains 1 e- =GER
• Cl gains e- (GER) so Cl gets reduced • Cl caused Na to get oxidized• Cl is the Oxidizing agent
5 - 39CH110:
H2OH2O
more stablemore stable
Energy in Chemical Reactions
Exothermic reactionExothermic reaction
-H= heat of reaction
En
erg
y
Rxn Progress
Reactants
Products
Eact= Activation Energy
(Gets hot)(Gets hot)
H2 + O2H2 + O2
2H2 + O22H2 + O2 2H2O + Energy2H2O + Energy
5 - 40CH110:
Exothermic ReactionsE
ner
gy
Rxn Progress
2Mg + O2 2MgO + Energy
2H2 + O2 2H2O + Energy
CH4 + 2O2 CO2 + 2H2O + 213 kcal
5 - 42CH110:
more stablemore stable
Energy in Chemical Reactions
Endothermic reactionEndothermic reaction
+H= heat of reactionEn
erg
y
Rxn Progress
Reactants
Products
Eact= Activation Energy
(Gets cold)(Gets cold)
5 - 44CH110:
En
erg
y
Rxn Progress
2H2(g) + O2(g) 2H2O + Energy2H2(g) + O2(g) 2H2O + Energy
Just because something has the potential to react doesn’t mean it will do so immediately.Just because something has the potential to react doesn’t mean it will do so immediately.
H2(g) + O2(g) may
stay together for
lifetime without
reacting to form
water.
H2(g) + O2(g) may
stay together for
lifetime without
reacting to form
water.
Reaction Rates
5 - 45CH110:
Oxidation: Paper burning Oxidation: Paper burning
Paper turning yellowPaper turning yellow
Oxidation: Nails rustingOxidation: Nails rusting
Reaction Rates
Fast:
Slow:
5 - 46CH110:
Rates of Reactions
Reaction rates can be affected by :Assuming reactant structure favor reaction
(polar vs. nonpolar) (vapor vs liq.)
1. temperature (hypothermia & metabolism)
2. concentration of reactants (medications)surface area (sugar cube vs crystals)
3. catalyst (H2O2 & blood)
5 - 47CH110:
They have to have enough E.
Reaction Rates
For reactants to make products:
•Molecules must collide
(solvents really help)
•They have to be aligned correctly.
(Parked cars don’t collide)
5 - 48CH110:
Reaction RatesFactors that increase reaction rate:
1. Higher Temperature:
Faster cars More collisions
More Energy More collisions
5 - 49CH110:
Reaction Rates
Factors that increase reaction rate:2. Increased Concentration: More Reactants
More cars More collisions
8 blocks:34 surfaces
8 blocks:24 surfaces
More surface area More collisions
5 - 50CH110:
Reaction Rates
Factors that increase reaction rate:3. Adding a Catalyst:
Lower Eact More collisions
Uncatalysed reactionUncatalysed reaction
5 - 51CH110:
Reaction Rates
Factors that increase reaction rate:3. Adding a Catalyst:
Lower Eact More collisions
Uncatalysed reactionUncatalysed reaction
Catalysed reactionCatalysed reaction
Lower activation energy
5 - 52CH110:
Alter the reaction mechanism but not change the products
Uncatalysed reactionUncatalysed reaction
Catalysed reactionCatalysed reaction
Lower activation energy
A catalyst will:
Enzymes are biological catalysts.Enzymes are biological catalysts.
Catalysts