Download Chapter 10.1

Chapter 10.1
Chemical Equations
Chemical Reaction
• Process by which one or more
substances are changed into
new substances
• Evidenced by changes in:
temperature, color, odor, gas
bubbles, precipitates, etc.
Chemical Equation
Represents a chemical reaction and
relative amounts
Correct equation tells us:
1. What changed – Reactants
2. What’s produced – Products
3. How much of each is involved
4. Physical state of each substance
Types of Equations
1. Word Equations – sentence that
describes equation
Gaseous hydrogen combined with
gaseous oxygen produces liquid
water.
Types of Equations
2. Skeleton Equations – Uses
chemical formulas instead of
words
Practice Problems (p.279)
1. H2(g) + Br2 (g)  HBr (g)
2. CO (g) + O2 (g)  CO2 (g)
3. KClO3 (s)  KCl (s) + O2 (g)
Balanced Chemical
Equation
• A chemical equation that has the
same number of atoms, of each
element, on both sides of the
equation
• Requirement of the Law of
Conservation of Mass
• Flow Chart on page 283
Balancing Equations
1.Describe the reaction, putting
reactants on the left and products on
the right
2.Write the equation using symbols
and formulas
3.Check for Balance using lowest
possible ratio
4.Adjust coefficients to get equal
numbers of each type of atom
Helpful Hints
1. Never touch subscripts when
balancing equations.That will change
the composition and therefore the
substance itself.
2. Check to be sure that you have
included all sources of a particular
element that you are balancing on a
particular side. There may be two or
more compounds that contain the
same element on a given side of an
equation.
Helpful Hints
3. Adjust the coefficient of lone
elements near the end of the
balancing act since any change in
their coefficient will not affect the
balance of other elements
4. Diatomic elements (H,N,O, &
Group 17) always appear as 2
atoms i.e O2
Chapter 10.2
Types of Reactions
Single Replacement
One element displaces another
element
E+CE+C
A + BC  B + AC
Mg + 2 H2O  Mg(OH)2 + H2
Single Replacement
1. A metal will not always replace
another metal in an aqueous
compound
2. Metal must be more reactive than
the metal it replaces (Fig. 10.10
p.288)
3. NR indicates no reaction takes place
4. Halogens only replace elements
below them on the periodic table
Double Replacement
One element replaces the like
charged element in a compound
C+CC+C
AB + CD  AD + CB
Pb(NO3)2 + 2 KI  PbI2 + 2 KNO3
Always produce a precipitate, gas,
and/or water
Decomposition
• Breaking a compound into its
component parts
• Energy must be added
C E+E
AB  A + B
2 H2O  2 H2 + O2
Decomposition
Compounds break down as follows:
1. Binary Compound  2 elements
2. Acids  Acidic Oxide + Water
3. Metallic Hydroxide  Metallic Oxide
+ Water
4. Metallic Carbonate  Metallic Oxide
+ Carbon Dioxide
Decomposition
5. Metallic Chlorate  Metallic Chloride
+ Oxygen
6. Metallic Oxides  Metal + Oxygen
Synthesis
Two or more substances combine to
form a new substance
E+EC
A + B  AB
8 Fe + S8  8 FeS
Not a practical method for creating
compounds
Combustion
Compounds formed by burning
• Oxygen is always involved
CxHy + O2  CO2 + H2O
C3H8 + 5O2  3CO2 + 4H2O
• Release energy as heat and light