1. Chapter 11: Chemical Reactions
chemical reaction: the process by which one or more substances are changed into one or more different substances.
in a reaction: REACTANTS PRODUCTS
Exothermic
Heat/Light
Indications of a Chemical Reaction
Evolution of heat and light
Production of a gas
Formation of a precipitate (insoluble solid)
Gas
Produced
Precipitate
Word and Formula Equations
rewrite formulas into an equation showing reactants and products.
sodium oxide and water yields sodium hydroxide

2. Na2O + H2O  NaOH
Lead(II)chloride added to sodium chromate produces lead(II)chromate and sodium chloride
PbCl2 + Na2CrO4  PbCrO4 + NaCl
Beware of diatomic molecules!!!!!
H2 O F2 Br2 I2 N Cl2
Additional notations to consider:
Solid  (s) liquid  (l) gas  (g) aqueous  (aq)

3. 5 different types of reactions
Combination/ Synthesis
Decomposition
Single replacement/ displacement
Double replacement/ displacement
Combustion

4. Types of reactions
A combination reaction is a chemical change in which two or more substances react to form a single new substance.
A decomposition reaction is a chemical change in which a single compound breaks down into two or more simpler products
A single-replacement reaction is one in which one element replaces a second element in a compound

5. Types of Reactions(continued)
This is an example of a double-replacement reaction, which is a chemical change involving an exchange of positive ions between two compounds
A combustion reaction is a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light.

6. Combination/ Synthesis
Magnesium metal and oxygen gas combine to form the compound magnesium oxide.
2Mg(s) + O2 → 2 MgO(s)

7. 2HgO(s) ___________> 2Hg(l) + O2(g)
Decomposition
When mercury(II) oxide is heated, it decomposes or breaks down into two simpler substances.
2HgO(s) ___________> Hg(l) + O2(g)

8. Single Replacement Reaction
Dropping a small piece of potassium into a beaker of water creates the vigorous reaction.
2K(s) + 2H2O(l) → 2KOH(aq) + H2

9. Double Replacement Reaction
2KI(aq) + Pb(NO3)2(aq) → PbI2 + 2KNO3(aq)
2KI(aq) + Pb(NO3)2(aq) → PbI2 + 2KNO3(aq)

10. Combustion reaction
The complete combustion of a hydrocarbon produces carbon dioxide and water.
But if the supply of oxygen is limited during a reaction, the combustion will not be complete. It forms carbon monoxide instead of carbon dioxide.

11. Combustion Reactions
The complete combustion of a hydrocarbon releases a large amount of energy as heat
That’s why hydrocarbons such as methane (CH4), propane (C3H8), and butane (C4H10) are important fuels.
CH4(g) O2(g) → CO2(g) + 2H2O(g)
2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(g)

12. Activity series and single replacement reactions
activity series: a list of elements in order of decreasing activity; the activity series of halogens is Fl, Cl, Br, I
Higher the position of the element in the series, higher is its activity.
Aluminum can displace copper from its solution but copper cannot displace zinc from its solution.

13. Activity Series of the Elements
Activity of metals
Activity of halogen nonmetals F2
Cl2
Br2 I2 Li Rb K Ba Sr Ca Na
React with cold water
and acids, replacing
hydrogen. React with
oxygen, forming oxides. Mg Al Mn Zn Cr Fe Cd
React with steam (but
Not cold water) and acids,
Replacing hydrogen.
React with oxygen forming
oxides.