1. Chemical Reactions
Defn: Chemical Reaction- the process by which one or more substances are changed into one or more different substances.
Defn: Reactants: the original substance in a reaction.
Defn: Products: the substance produced.
Defn: Chemical Equation: represents with symbols and formulas the identities and relative molar amounts of the reactants and products in the reaction.

2. 7.3 The Chemical Equation: Use these abbreviations to add states to the equation.

3. Indication of a Chemical Reaction
Release of energy as both heat and light:
-- heat or light by itself is not necessarily a sign of chemical change, it could be only be a physical change.
2. Production of a gas:
-- the release of gas bubbles when substances are mixed is often evidence of a chemical change.
Formation of precipitate:
--Defn: precipitate: A solid produced as a result of a chemical reaction in solution in which the solid separates from the solution.
4. Color Change:
-- a change in color usually indicates a chemical change.

4. Characteristics of Chemical Equations
1. The equation must represent known facts.
2. The equation must contain known facts:
example---diatomic molecules must be written correctly
O₂ H₂ N₂ F₂ Cl₂ Br₂ and I₂
3. The law of conservation of mass must be satisfied using correct coefficients.
Defn: Coefficient: a small whole number that appears in front of a compound or element in a chemical equation.

5. Significance of Chemical Equation
Defn: Word Equation: An equation in which reactants and products in a chemical reaction are represented by words.
Defn: Formula Equation: represents reactants and products in an equation by their formula; not always balanced.
Defn: Chemical Equation: A formula equation that is balanced.
Significance of Chemical Equation
The coefficients indicate relative not absolute amounts of reactants and products
----usually shows the smallest number of atoms, molecules, or ions.
2. The relative masses of the reactants and products of a chemical reaction can be determined from the reaction ‘s coefficients.
3. The reverse reaction for a chemical equation has the same relative amounts of a substance as the forward reaction.
Defn: Reversible reaction: a chemical reaction in which the products re-form the original reactants.

6. Balancing Chemical Equations
Defn: Catalyst: A substance that changes the rate of a chemical reaction but is recovered unchanged at the end of the reaction.
Balancing Chemical Equations
1. Identify the names of the reactants and the products and write a word equation.
2. Write a formula equation by substituting correct formulas for the names.
3. Balance the formula Equation
1. Balance individual atoms one at a time
2.Balance atoms that appear alone on one side of the equation first
3. Balance polyatomic compounds next
4. Balance O and H last
4. Count all atoms(elements) to be sure that the equation is balanced
***Never change the subscript of chemical formulas because that would change the chemical identity***

7. 7.3 The Chemical Equation: Combustion of Methane
To balance an equation, we insert coefficients—not subscripts—in front of the chemical formulas as needed to make the number of each type of atom in the reactants equal to the number of each type of atom in the products.
The equation is now balanced because the numbers of each type of atom on both sides of the equation are equal.

8. Example: Write a balanced equation for the reaction of solid aluminum with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas.
Use your knowledge of chemical nomenclature from Chapter 5 to write a skeletal equation containing formulas for each of the reactants and products.
The formulas for each compound MUST BE CORRECT before you begin to balance the equation.

9. Example: The reaction of solid aluminum with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas.
Since both aluminum and hydrogen occur as pure elements, balance those last.
Sulfur and oxygen occur in only one compound on each side of the equation, so balance these first.
Sulfur and oxygen are part of a polyatomic ion that stays intact on both sides of the equation.
Balance polyatomic ions such as these as a unit.
There are 3 SO42- ions on the right side of the equation, so put a 3 in front of H2SO4.

10. Example: The reaction of solid aluminum with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas.
Balance Al next. Since there are 2 Al atoms on the right side of the equation, place a 2 in front of Al on the left side of the equation.
Balance H next. Since there are 6 H atoms on the left side, place a 3 in front of on the right side.

11. Example: The reaction of solid aluminum with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas.
Sum the number of atoms on each side to make sure that the equation is balanced.

12. Example 7.5 Balancing Chemical Equations
Balance this chemical equation.
Fe(s) + HCl(aq)  FeCl3(aq) + H2(g)
Since Cl occurs in only one compound on each side of the equation, balance it first. There is 1 Cl atom on the left side of the equation and 3 Cl atoms on the right side. To balance Cl, place a 3 in front of HCl.
Since H and Fe occur as free elements, balance them last. There is 1 Fe atom on the left side of the equation and 1 Fe atom on the right, so Fe is balanced. There are 3 H atoms on the left and 2 H atoms on the right. Balance H by placing a in front of (That way you don’t alter other elements that are already balanced.)
Since the equation now contains a coefficient fraction, clear it by multiplying the entire equation (both sides) by 2.
SOLUTION
Fe(s) + 3 HCl(aq)  FeCl3(aq) + H2(g) 3 2

13. Example 7.5 Balancing Chemical Equations
Continued
Finally, sum the number of atoms on each side to check that the equation is balanced.
2 Fe(s) + 6 HCl(aq)  2 FeCl3(aq) + 3 H2(g)
Reactants Products
2 Fe atoms  2 Fe atoms
6 Cl atoms  6 Cl atoms
6 H atoms  6 H atoms
SKILLBUILDER 7.5 Balancing Chemical Equations
Balance this chemical equation.
HCl(g) + O2(g)  H2O(l) + Cl2(g)
Answer: 4 HCl(g) + O2(g)  2 H2O(l) + 2 Cl2(g)
For More Practice Problems 45, 46, 47, 48, 49, 50.

14. 7.5 Aqueous Solutions and Solubility: Compounds Dissolved in Water
A compound is soluble in a particular liquid if it dissolves in that liquid.
A compound is insoluble if it does not dissolve in the liquid.
An aqueous solution is a homogeneous mixture of a substance with water.
When ionic compounds dissolve in water, they usually dissociate into their component ions.

15. TABLE 7.2 Solubility Rules

16. TYPES OF CHEMICAL REACTIONS Types of synthesis reactions
Defn: Synthesis Reaction- Two or more substances combine to form a new compound. A +X  AX
Types of synthesis reactions
Oxygen and Sulfur
-both react with groups 1 and 2 to form oxides and sulfide
-almost all metals react with oxygen
-most non-metals react with oxygen in synthesis reactions
Metals and Halogens:
-most metals react with halogens in a synthesis reaction
-oxides in reactive metals undergo synthesis. Example calcium oxide and water.

17. Types of single displacement
Defn. Decomposition Reaction: A single compound undergoes a reaction that produces two or more simple substances. AX  A + X
Defn. Electrolysis: decomposition of a substance by an electric current. Example water.
Defn. Single Displacement: One element replaces a similar element in a compound. A + BX  B + AX
Types of single displacement
1. Displacement of a metal with another metal
2. Displacement of hydrogen in water by a metal
3. Displacement of hydrogen in an acid by a metal
4. Displacement of a halogen by a more reactive halogen

18. Defn. Double Displacement: The ions of two compounds exchange places in an aqueous solution to form a new compound.
AX + BY  AY + BX
This is what usually forms a precipitate or gas bubble.
Defn. Combustion Reaction: A substance combines with oxygen releasing a large amount of energy in the form of heat and light.
Reaction types:
Synthesis
Decomposition
Single displacement
Double displacement
Combustion

19. Writing Equations for Precipitation Reactions
1. Write an equation for the precipitation reaction that occurs (if any) when solutions of sodium carbonate Na2CO3(aq) and copper(II) chloride CuCl2(aq) are mixed. 2. Combine the cation from one reactant with the anion from the other.

20. Writing Equations for Precipitation Reactions
Make sure to write correct (charge neutral) formulas for the new ionic compounds.
3. Use the solubility rules to determine whether any of the potential new products are indeed insoluble.
Potentially Insoluble Products:
NaCl CuCO3
NaCl is soluble (compounds containing Cl− are usually soluble and Na+ is not an exception).
CuCO3 is insoluble (compounds containing CO32− are usually insoluble and Cu2+ is not an exception).

21. Writing Equations for Precipitation Reactions
4. If all of the potentially insoluble products are soluble, there will be no precipitate. Write NO REACTION next to the arrow.
5. One of the potentially insoluble products is insoluble, so write its formula as the product of the reaction, using (s) to indicate solid. Write the soluble product with (aq) to indicate aqueous.
Na2CO3(aq) + CuCl2(aq)  CuCO3(s) + NaCl(aq)

22. Writing Equations for Precipitation Reactions
6. Balance the equation.
Remember to adjust only the coefficients, not the subscripts.
Na2CO3(aq) + CuCl2(aq)  CuCO3(s) + 2NaCl(aq)

23. 7.7 Writing Chemical Equations for Reactions in Solution: Complete Ionic and Net Ionic Equations
In the complete ionic equation, some of the ions in solution appear unchanged on both sides of the equation.
These ions are called spectator ions because they do not participate in the reaction.

24. Ag+(aq) + Cl− (aq)  AgCl(s)
7.7 Writing Chemical Equations for Reactions in Solution: Complete Ionic and Net Ionic Equations
To simplify the equation, and to more clearly show what is happening, spectator ions can be omitted.
Equations such as this one, which show only the species that actually participate in the reaction, are called net ionic equations.
Ag+(aq) + Cl− (aq)  AgCl(s)

25. 7.8 Acid–Base Reactions
Acid–base reactions are reactions that form water upon mixing of an acid and a base.

26. H+(aq) + OH− (aq)  H2O(l)
7.8 Acid–Base Reactions
Acid–base reactions
(also called neutralization reactions)
generally form water and an ionic compound—called a salt—that usually remains dissolved in the solution.
The net ionic equation for many acid–base reactions is:
H+(aq) + OH− (aq)  H2O(l)

27. 7.8 Acid–Base Reactions: Some Common Acids and Bases

28. 7.9 Oxidation–Reduction Reactions
Reactions involving the transfer of electrons are called oxidation–reduction reactions or redox reactions.
Redox reactions are responsible for the rusting of iron, the bleaching of hair, and the production of electricity in batteries.
Many redox reactions involve the reaction of a substance with oxygen.
Many redox reactions involve transition metals.

29. 7.9 Oxidation–Reduction Reactions
A fundamental definition of oxidation is the loss of electrons.
A fundamental definition of reduction is the gain of electrons.
Helpful mnemonics:
OIL RIG—Oxidation Is Loss; Reduction Is Gain.

30. 7.10 Classifying Chemical Reactions by What Atoms Do

31. Classification Flow Chart