Chapter 11 Chemical Reactions

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Chapter 11 Chemical Reactions
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Hindenburg Ship
Hydrogen gas combined with Oxygen which caused
the ship to catch fire
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Chemical reactions
Take place after you eat
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Photosynthesis
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In a Chemical reaction
One or more substances change into one or more
new substances
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Writing chemical equations
Word Equations
Reactants
Products
Iron Oxygen
Iron(III) Oxide
Hydrogen Peroxide
Water Oxygen
Methane oxygen
Carbon dioxide water
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Chemical Equations
Skeleton Equations
Fe O2
Fe2O3
- Equation that does not show the amounts of the
reactants and the products
Unbalanced equation !!!!!
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To add more information to the skeleton equations
To indicate if the reactants and products are
liquids, solids or gases you use parentheses
Fe(s) O2(g)
Fe2O3 (s)
To indicate a catalyst (a substance that speeds
up the reaction but is not used in the reaction)
you place the catalyst over the arrow
MnO2
H2O2 (aq)
H2O (l) O2 (g)
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Symbol Explanation
Used to separate two reactants or two products
yields
Reaction is reversible
(s) Solid state
(l) Liquid state
(g) Gaseous state
(aq) Aqueous solution, dissolved in water
Heat is applied to reaction
Catalyst used in reaction
heat
catalyst
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Balancing Equations
Reactants
Products
Frame wheel hanlebar pedal
Bicycle
F 2 W 1 H 2 P
FW2HP2
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Carbon Oxygen
Carbon Dioxide
First write the skeleton equation
C O2
CO2
Now balance
C O2
CO2
1 C
1 C
2O
2O
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Hydrogen gas oxygen gas
Water
First write the skeleton equation
H2 (g) O2 (g)
H2O
Now balance
2 H
2 H
2 X
2 O
1 O
X 2
Balanced!!
2H2(g) O2
2H2O
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Types of Chemical Reactions
5 Types
combination
decomposition
Single-replacement
Double-replacement
combustion
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Combination Reactions
(Synthesis)
Chemical change in which two or more substances
react to form a single new substance
2 Mg(s) O2(g)
2 MgO(s)
Metal nonmetal
2 K(s) Cl2(g)
2 KCl(s)
SO2 (g)
S (s) O2(g)
Two nonmetals two possibilities
2 S (s) 3 O2(g)
SO3 (g)
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Decomposition Reactions
Chemical change in which a single compound breaks
down into two or more simpler products
2 HgO(s)
2 Hg(l) O2(g)
heat
electricity
2 H2O(l)
2 H2(g) O2(g)
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Single-replacement Reactions
Chemical change in which one element replaces a
second element in a compound
2 K(s) 2 H2O(l)
2 KOH(aq) H2(g)
Zn(s) H2SO4(aq)
ZnSO4(aq) H2(g)
Cl2(g) 2 NaBr(aq)
2NaCl(aq) Br2(aq)
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Double-replacement Reactions
Chemical change involving an exchange of positive
ions between two compounds
2 NaCN(aq) H2SO4(aq)
2 HCN(aq) Na2SO4(aq)
NaOH(aq) Fe(NO3)3 (aq)
Fe(OH)3(s) 3 NaNO3(aq)
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Combustion Reactions
Chemical change in which an element or compound
reacts with oxygen often producing energy in the
form of heat or light
CH4 (g) 2 O2(g)
CO2 (g) 2 H2O(l)
2HCOOH (aq) O2(g)
2CO2 (g) 2 H2O(l)
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The number of elements and/or compounds
reacting is a good indicator of possible reaction
types and possible products- you can make
predictions
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Check what you know!!

• What are the five different types of reactions?
• What type of reaction are the following?
• C3H6 O2 ? CO2 H2O
• Li O2 ? Li2O
• Zn AgNO3 ? Ag Zn(NO3)2

Combination, decomposition, single-replacement,
double-replacement, combustion
Combustion
Combination
Single-replacement
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• Predict the type of reaction that will occur?
• An aqueous solution of two ionic compounds.
• Reactant is a single compound.
• The reactants are two elements.
• The reactants are oxygen and a compound of carbon
  and hydrogen.

Double-replacement
Decomposition
Combination
Combustion
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Reactions in Aqueous Solution
Net Ionic Equations Many important reactions
take place in water
Net ionic equations are different that the
equations we are used to writing. We used to
write equations like this
AgNO3(aq) NaCl(aq) ? AgCl(s) NaNO3(aq)
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Complete Ionic Equations
Shows the dissolved ionic compound as separate
ions
Ag(aq) NO3-(aq) Na(aq) Cl-(aq)
AgCl(s) Na(aq) NO3- (aq)
Spectator ions -
Ion that appears on both sides of the equation
but is not involved in the reaction
Net Ionic Equations
Equation that shows only the particles that are
directly involved in the reaction
Ag(aq) Cl-(aq)
AgCl(s)
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Predicting the formation of a precipitate
Compounds Solubility
Salts of alkali metals and ammonia Soluble
Nitrate salts and chlorate salts Soluble
Sulfate salts, except compounds with Pb, Ag, Hg, Ba, Sr, Ca Soluble
Chloride salts except compounds with Ag, Pb, Hg Soluble
Carbonates, phosphates, chromates, sulfides and hydroxides Insoluble
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Will a precipitate form when aqueous solutions of
Na2CO3(aq) and Ba(NO3)2(aq) are mixed?
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Check what you know!!!

• Write a balanced net ionic equation.
• Pb(NO3)2(aq) H2SO4(aq) ? PbSO4(s) HNO3(aq)

First write the complete ionic equation
Pb2(aq) NO3- (aq)
H(g) SO42-(aq)
PbSO4(s)
H(g) NO3- (aq)
Then find the spectator ions and cross them out
Finally, write the net ionic equations
Pb2(aq)
SO42-(aq)
PbSO4(s)