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Balancing Chemical Equations

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Chapter 7 Balancing Chemical Equations Chemical Reaction Describes chemical reaction. Chemical equation: reactants yield products Symbols Used (s) solid (l ... – PowerPoint PPT presentation

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Title: Balancing Chemical Equations


1
Chapter 7
  • Balancing Chemical Equations

2
Chemical Reaction
  • Describes chemical reaction.
  • Chemical equation reactants yield products

Catalyst substance that speeds up a reaction
without being used up.
3
Symbols Used
  • (s) solid
  • (l) liquid
  • (g) gas
  • (aq) aqueous (in water solution)
  • gas as a product
  • ppt. (precipitate)
  • D means with heat
  • Pt means with Platinum catalyst

4
Balancing Chemical Equations
  • Balanced equations have the same of atoms of
    each element on each side of the equation.
  • Law of Conservation of Mass atoms can neither
    be created nor destroyed, simply rearranged.

5
Rules for Balancing Equations
  • Get the correct formulas for reactants and
    products.
  • Write reactants on left, products on right and
    use plus signs and arrows when needed.
  • Count the of atoms of each element in reactants
    and products.(Polyatomic ions on both sides count
    as one.)
  • Balance of each element using coefficients.
  • Coefficient whole in front of a formula.

6
Rules for Balancing Equations
  • Check each element to make sure equation is
    balanced.
  • Make sure all coefficients are in the lowest
    whole number ratio.

Do not change subscripts!!!
7
Diatomic Molecules
  • Diatomic Molecules- a molecule made up two atoms
    of the same element. They are only diatomic when
    they are alone.
  • There are 7 naturally occurring
  • diatomic molecules.

H O N Cl Br I F
8
5 Types of Reactions - 1
  • Combination Reaction elements combine to form a
    compound.
  • A B AB

9
Examples of Combination Reactions
1. 2 Na Cl2 2 NaCl
2
2. Cu S Cu2S
3. SO3 H2O
H2SO4
4. CaO H2O
Ca(OH)2
2
MgO
5. Mg O2
2
10
5 Types of Reactions - 2
  • Decomposition Reaction elements break down into
    its element.
  • AB A B

11
Examples of Decomposition Reactions
1. 2 NaCl 2 Na Cl2
2
2
2. H2O H2 O2
2
3. HgO
Hg O2
2
Challenge Copper I Chloride Decomposes
2CuCl 2Cu Cl2
12
5 Types of Reactions - 3
  • Single Replacement Reaction one element
    replaces another element in a compound.
  • AB C A CB
  • or
  • AB D AD B

-
-
- -
- -
13
Reactivity Series of Metals and Non-Metals
  • The single metallic element will only replace the
    metal in a compound if it is more reactive.
  • A chart is used to determine if the lone metal is
    more reactive. If not, no reaction occurs.
  • The single non-metallic element will only replace
    the non-metal in a compound if it is more
    reactive. The higher up in the group the
    non-metal is, the more reactive it is.

14
Examples of Single Replacement Reactions
1. Zn H2SO4 ZnSO4 H2
2. K HOH KOH H2
NaCl Br2
2
2
3. Cl2 NaBr
15
5 Types of Reactions - 4
  • Double Replacement Reaction two compounds react
    and exchange positive ions to form two new
    compounds.
  • AB CD AD CB

- -
- -
16
Examples of Double Replacement Reactions
1. NaOH H2SO4 Na2SO4 HOH
2
2
2. BaCl2 K2CO3 BaCO3 KCl
2
3. FeS HCl
2
H2S FeCl2
17
5 Types of Reactions - 5
  • Combustion Reaction oxygen reacts with a
    compound composed of C and H.
  • CxHy O2 CO2 H20

Also called Burning (exothermic) The products are
always CO2 and H2O.
18
Examples of Combustion Reactions
1. C6H6 O2 CO2
H2O
3
6

C6H6 O2 CO2 H2O
2 15 12
6
2. CH3OH O2 CO2 H2O
2

CH3OH O2 CO2 H2O
2 3 2
4
19
Special Decomposition Reactions 1
  • Decomposition of a Carbonate
  • XCO3 XO CO2
  • ex. Na2CO3 Na2O CO2

20
Special Decomposition Reactions 2
  • Decomposition of a Hydroxide
  • XOH XO H2O
  • ex. 2NaOH Na2O H2O

21
Special Decomposition Reactions 3
  • Decomposition of a Chlorate
  • XClO3 XCl O2
  • ex. NaClO3 NaCl O2

22
Special Decomposition Reactions 4
  • Special single Replacement Reaction
  • Group IA or IIA metal and H2O
  • X HOH XOH H2
  • ex. 2Na 2HOH 2NaOH H2

23
How to ID types of reactions.
  • Combination Reactions given 2 items that form 1
    new compound.
  • Decomposition Reactions given a single compound
    that breaks into parts.
  • Single Replacement given a single element plus
    a single compound, forms a new compound a a
    different element.
  • Double Replacement given two compounds (s or
    s change places).
  • Combustion Reaction given CH compound with
    Oxygen, always forms water and carbon dioxide.

24
The End
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