1. Types of Chemical Reactions

2. How do I tell if a reaction has occurred?
Signs of a chemical reaction
Temperature change
Release of light
Color change
Appearance of precipitates (solids)
Gas/odor released

3. How do I represent a chemical rxn?
Reactant Reactant 2  Product Product 2
Reactants are starting substances.
Products are substances formed.
Arrow shows direction of progress.
A “+” sign is placed between reactants and products to separate them.

4. How do I represent a chemical rxn?
Na (s) + H2O (l)  NaOH (aq) + H2 (g)
Symbols are used behind each substance to show physical state of reactants and products –
(s) solid
(l) liquid
(g) gas
(aq) dissolved in water.

5. How do I represent a chemical rxn?
Solids as products are known as precipitates
Aqueous products are produced if there was water present as a reactant (either water itself was a reactant or an aqueous solution was a reactant)

6. Subscripts and Coefficients
What does a subscript mean in a chemical formula?
Ex. Al2O3, H3PO4, Na2SO4
Number of atoms in a formula

7. Subscripts and Coefficients
What does a coefficient mean written in front of an element or formula?
How many of the element or compounds/molecules there are present in the reaction

8. Word & Skeletal Equations
A) Word equations:
reaction written with words instead of chemical symbols.
Ex. Magnesium (s) + Oxygen (g)  Magnesium oxide (s)
Magnesium reacts with oxygen to produce magnesium oxide.

9. Word & Skeletal Equations
B) Skeleton Equations:
Use chemical formulas and symbols instead of words – not balanced.
Ex. Mg(s) + O2(g)  MgO(s)

10. III. Conservation of Mass
-matter is neither created or destroyed in a chemical reaction.
-number of atoms in reactant equals number of atoms in product.
-sum of mass in reactant equals sum of mass in product.
Ex. 2H2O2  2H2O + O2
68.0g g + _?_
68.0g – 32.0g = 36.0 g

11. Balancing Chemical Equations
We use coefficients in front of reactants and products – usually whole numbers – and tells you the smallest # of particles involved in the reaction.
Steps:
Write skeleton equation.
Count the # of elements in reaction.
Change the coefficients to make the # of atoms of each element equal on both sides of the equation.
Write the coefficients in their lowest possible ratio.
Check your work.

12. Practice
_____ H2 + _____O2 → _____H2O
Hydrogen and nitrogen gas react to form nitrogen trihydride.
_____Al2O3 → _____Al + _____O2
Potassium chlorate breaks down to form potassium chloride and oxygen gas
Octasulfide + oxygen gas → sulfur dioxide

13. Dicarbon hexahydride react with oxygen gas to produce carbon dioxide and water.
Aluminum sulfate + calcium hydroxide → aluminum hydroxide + calcium sulfate
­­­­­_____P4 + _____O2 → _____P2O5
_____Ag + _____S8 → _____Ag2S
10. Aluminum and liquid Bromine combine to form Aluminum bromide.

14. There are five types: Synthesis Decomposition Single-replacement
Double-replacement
Combustion

15. 1. Synthesis (redox)
Two or more elements or compounds that combine to form a single substance either ionic or covalent.
General equation: A + B  AB
EX. Iron and chlorine combine to produce Iron (III) chloride.
2Fe (s) + Cl2 (g)  2FeCl3 (s)

16. Synthesis Special Cases
Non-metal oxide + water  acid
Use oxidation numbers to find the oxidation number of the non-metal.
Use the oxidation number of the non-metal to determine the oxyanion of the acid.
Must balance charges from the ions when you write the formula for the acid.
Example: SO2 + H2O  H2SO3
Non-metal oxide + metal oxide  salt
Use the oxidation number of the non-metal to determine the oxyanion of the salt. The cation is the metal ion.
Must balance charges from the ions when you write the formula for the salt.
Examples:
CO2 + metal oxide  metal carbonate
SO2 + metal oxide  metal sulfite
SO3 + metal oxide  metal sulfate
metal oxide + water  base
The metal is the cation of the base.
The anion is OH-1 (definition of a base).
Must balance charges from the ions when you write the formula for the base.
Example: Al2O3 + H2O  Al(OH)3
Look at back of pink periodic table sheet!!!

17. 2. Decomposition
A single compound is broken down into two or more substances.
Opposite of synthesis.
General equation: AB A + B
EX. Hydrogen peroxide decomposes into water and oxygen.
2H2O2 (aq)  O2 (g) + 2H2O (l)

18. Decomposition Special cases
acid  Non-metal oxide + water
salt  Non-metal oxide + metal oxide
Uses the oxidation steps from the combination reactions in reverse.
Find the oxidation number of the non-metal in the oxyanion.
Use the oxidation number of the non-metal to determine the formula of the non-metal oxide.
Must balance charges from the ions when you write the formula for the metal oxide. The metal cation is the metal from the salt.
Metal halate  metal halide + oxygen gas
Metal carbonate  metal oxide + carbon dioxide
Metal peroxide  metal oxide + oxygen gas
Look at back of pink periodic table sheet!!!

19. 3. Single replacement
One element replaces a second element in a compound.
Single metal replaces metal in compound
Single nonmetals replaces nonmetal in compound
General equation: A + BX  AX + B (metal)
Q2 + RS  RQ + S2 (nonmetal)

20. 3. Single replacement EX. 2AgNO3 (aq) + Cu(s)  2Ag(s) + Cu(NO3)2 (aq)
Silver nitrate reacts with copper to produce silver and copper (II) nitrate
Single replacement ONLY OCCURS if single element is more active than the element its replacing in compound
Look at back of pink periodic table

21. 4. Double replacement
Involves an exchange of positive ions between two reacting compounds. Reactants are two ionic compounds
AX + BY  A Y + B X

22. 4. Double replacement
Double replacement ONLY OCCURS if one of the following applies:
One product precipitates from solution or
One product is a gas and bubbles out of solution or
One product is a molecular compound such as water
Ex. AgNO3 (aq) + NaCl (aq)  AgCl (s) + NaNO3 (aq)

23. Double Replacement Special cases:
Acid-Base neutralization reactions:
Acid + Base  Salt + water
Acid: Cation = H+
Base: Anion = OH-1
Salt: Anything that can be made from an acid and a base that is not water.

24. Double Replacement Special cases:
Gas forming reactions:
Acid + metal carbonate  salt + water + carbon dioxide
*Double replacement reaction that produces H2CO3
- H2CO3 breaks down as soon as it forms. Follows the
rules for metal carbonate decomposition.
Acid + metal sulfate  salt + water + sulfur dioxide
-Same type of problem as the acid + metal carbonate.

25. 5. Combustion
An element or compound reacts with oxygen, often producing energy as heat or light.
CxHyOz + O2  CO2 + H2O
Some synthesis (combination) reaction fall under this category.
General form…you get the oxide of every element you burn (except oxygen).
Complete combustion is excess oxygen…gives you CO2 as the oxide of carbon.
Incomplete combustion is limited oxygen…gives you CO as the oxide of carbon.