chapter 11
DESCRIPTION
Chapter 11. Chemical Reactions. Chemical Equation. Describes chemical reaction. Chemical equation: reactants yield products Reactants Products Much easier to write symbols and formulas instead of words. Examples. Solid Iron reacts with oxygen gas to form the solid IronIIIoxide . - PowerPoint PPT PresentationTRANSCRIPT
Chapter 11
Chemical Reactions
Chemical Equation
Describes chemical reaction. Chemical equation: reactants yield products
Reactants Products
Much easier to write symbols and formulas instead of words
Examples Solid Iron reacts with oxygen gas to form the solid
IronIIIoxide. iron(s) + oxygen(g) ironIIIoxide(s) Fe(s) + O2(g) Fe2O3(s)
Carbon tetrahydride gas BURNS to form carbon dioxide gas and water vapor.
Carbon tetrahydride(g) + oxygen(g) carbon dioxide(↑) + water(↑)
CH4(g) + O2(g) CO2(↑) + H2O(↑) Skeleton Equation: chemical equation that tells you what the
reactants and products are but NOT how much of each you have. First step in writing a chemical equation.
Symbols Used (s) solid (l) liquid (g) gas (↑) gas as a product (aq) aqueous (in water solution) () ppt (precipitate) solid product from 2
aqueous reactants D means with heat Pt means with Platinum catalyst: speeds up a
reaction without being used. reversible reaction
Balancing Chemical Equations
Balanced equations have: the same # of atoms of each element on
BOTH sides of the equation.
Law of Conservation of Mass – atoms can neither be created nor destroyed, simply rearranged.
Rules for Balancing Equations
Get the correct formulas for reactants and products.
(USE ION CHART AND DON”T FORGET DIATOMIC ELEMENTS!)
Write reactants on left, products on right. Use plus signs to separate compounds and yield sign to separate the reactants from products.
Rules Continued Count the # of atoms of each element in
reactants and products. (Polyatomic atoms on both sides count as one.)
Balance # of each element using coefficients.
Coefficient – small whole # in front of a formula.
NEVER CHANGE FORMULA SUBSCRIPTS
Rules for Balancing Equations
Balance elements appearing 3 or more places LAST.
Check each element to make sure equation is balanced.
Make sure all coefficients are in the lowest whole number ratio.
Do not change subscripts!!!
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
Balancing Examples
___ C(s) + ___ O2(g) ___ CO2 (g)
___ C(s) + ___ O2(g) ___ CO (g)
___ AgNO3(aq) + ___Cu(s) ___ Cu(NO3)2(aq) + ___ Ag(s)
___ Al(s) + ___ O3(g) ___ Al2O3(s)
*___ C2H6(g) + ___ O2(g) ___ CO2(g) + ___ H2O(g)
*___ H3PO3 ___ H3PO4 + PH3
5 Types of Chemical Reactions
Combination Reaction – elements combine to form a compound.
A + B AB element + element compound Ex. Sodium + chlorine sodium chloride ___Na(s) + ___ Cl2(g) ___ NaCl(s)2 2
5 Types of Reactions
Decomposition Reaction – compound
breaks down into its element. AB A + B compound element + element Ex: MercuryII oxide mercury + oxygen ___ HgO ___Hg + ___O22 2
5 Types of Reactions - 3
Single Replacement Reaction – one element replaces another element in a compound.
AB + C A + CBor
AB + D AD + B
+ - + + + -
+ - - + - -
Examples of Single Replacement Reactions
• Must use Activity Series to see if reaction works
• Zinc + sulfuric acid zinc sulfate + hydorgen
• Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(↑)
• Periodic table is activity series for halogens
• Sodium bromide + chlorine sodium chloride + bromine
• ___NaBr(s) + ___Cl2(g) ___NaCl(s) + ___Br2(↑)22
5 Types of Reactions
Double Replacement Reaction – two compounds react and exchange positive ions to form two new compounds.
AB + CD AD + CB Barium Chloride(aq) + potassium carbonate(aq)
barium carbonate() + potassium chloride(aq)
BaCl2(aq) + K2CO3(aq) BaCO3() + ___ KCl(aq)
+ - + - + - + -
2
5 Types of Reactions 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.
Examples of Combustion Reactions
1. C6H6 + O2 CO2 + H2O
2. CH3OH + O2 CO2 + H2O
367½
21½
CH3OH + O2 CO2 + H2O2 3 2 4
C6H6 + O2 CO2 + H2O 2 15 12 6
Special Decomposition Reactions:
Decomposition of a Carbonate: Metal carbonate metal oxide + carbon dioxide
XCO3 XO + CO2
ex. Na2CO3 Na2O + CO2
Special Decomposition Reactions:
Decomposition of a Hydroxide: Metal hydroxide metal oxide + water
XOH XO + H2O
ex. 2NaOH Na2O + H2O
Special Decomposition Reactions:
Decomposition of a Chlorate: (ClO3) Metal chlorate metal chloride + oxygen
XClO3 XCl + O2
ex. ___NaClO3 ___NaCl + ___O22 3
Special Decomposition Reactions: 4
Special single Replacement Reaction:»Group IA or IIA metal and H2O
X + HOH XOH + H2
ex. 2Na + 2HOH 2NaOH + H2
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 change places).
Combustion Reaction – given CH compound with Oxygen, always forms water and carbon dioxide.