1. CONCURRENT ENROLLMENT
CHAPTER 5
CONCURRENT ENROLLMENT

2. Chemical Reactions
Evidence that a chemical reaction may have occurred:
Change in temperature
Change in color
Odor
Gas bubbles
Appearance of a solid

3. CHEMICAL EQUATIONS This table summarizes the symbols used in
Reactants - are the starting substances.
Products - are the substances formed in the reaction.
This table summarizes
the symbols used in
chemical equations.

4. Law of conservation of matter
Balanced equation
An equation in which the number of atoms of each element in the reactants is the same as the number of atoms of that same element in the products

5. MASS RELATIONS IN REACTIONS
Writing a balanced equations
In a balanced equation you must conserve mass (atoms)
First you write a “skeleton” equation
CS2 + O2 ---> CO2 + SO2
Indicate the physical state
CS2(l) + O2(g) ---> CO2(g) + SO2(g)
Balance the equation
CS2(l) + 3O2(g) ---> CO2(g) + 2SO2(g)

6. THREE STEPS IN BALANCING
Determine the type of reaction. What are the reactants, products and physical states involved
Write a unbalanced equation
Balance equation, start with the most complicated molecule. Find the right coefficient to give the same number of each type of atom of both sides. DO NOT CHANGE THE IDENTITIES
(NH4)2 Cr2O7(s)----> Cr2O3(s) + N2(g) + H2O(g)

7. TYPES OF REACTIONS SYNTHESIS
When two elements react, the reaction is always a synthesis reaction.

8. DECOMPOSITION
A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds.
Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.
CaCO3 (s) –Δ CaO(s) + CO2(g)

9. SINGLE REPLACEMENT A metal will not always replace
a metal in a compound dissolved
in water because of differing
reactivities.
An activity series can be used to
predict if reactions will occur.
Halogens also have different
reactivities and do not
always replace each other.
Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)

10. DOUBLE REPLACEMENT occur when ions exchange between two compounds
Ca(OH)2(aq) + HCl(aq)  CaCl2(aq) + H2O(l) balance this
The solid product produced during a chemical reaction in a solution is called a precipitate.
All double replacement reactions produce either water, a precipitate, or a gas.

11. CONTINUED
COMBUSTION
oxygen combines with a substance and releases energy in the form of heat and light.

12. RULES FOR OXIDATION NUMBERS
Elements found in nature is always zero
Cu, O2
Monoatomic ions number is the same as its charge
Cl-, Mg2+
Fluorine always 1-
Oxygen 2-
Except with fluorine 2+
Peroxide 1-, H2O2
Superoxide ½ -, KO2
Hydrogen 1+
With group one elements then it is a hydride 1-
Sum of the oxidation numbers of ALL atoms in a neutral compound is zero
The most electronegative element in a binary compound oxidation number is the same as the ion charge
Sum of oxidation numbers of ALL atoms in a polyatomic ion is same as its charge

13. REDOX The concept of oxidation numbers explain oxidation and reduction
Oxidation increases the oxidation number (loss electrons)
Reduction decreases the oxidation number (gains electrons)

14. OXIDATION-REDUCTION REACTIONS
An oxidation-reduction reaction involves transfer of electrons
Addition of O2 or H2
What species goes through oxidation?
Species that lose electrons
What species goes through reduction?
Species that gain electrons
LEO goes GER
Cl-  Cl2
Cu+ + Al  Cu + Al3+
Oxidizing agent
The element accepts that the electron
Reducing agent
The element that gives the electron

15. ENERGY AND REACTION EXOTHERMIC REACTIONS
2H2(g) + O2(g)  2H2O(g) + heat
ENDOTHERMIC REACTIONS
2H2O(g) + heat  2H2(g) + O2(g)

16. CONTINUED Balancing redox equations Half-equation method
Split the equation into two half reactions
One for reduction and the other for oxidation
Balance one of the half-reactions with respect to both atoms and charge , use water to add oxygen’s, add hydrogen ions (in an acidic solution you will have both), add electrons to balance charge
Balance the half-reactions
Combine the two in such away as to eliminate all the electrons

17. Aqueous Solutions
An aqueous solution contains one or more dissolved substances (called solutes) in water.
The solvent is the most plentiful substance in a solution.
Ionic compounds can also be solutes in aqueous solutions
When ionic compounds dissolve in water, their ions separate in a process called dissociation
When two solutions that contain ions as solutes are combined, the ions might react.

18. If they react, it is always a double replacement reaction.
Three products can form: precipitates, water, or gases
Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide.
2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)
Ionic equations that show all of the particles in a solution as they actually exist are called complete ionic equations.
2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)

19. CONTINUED
Ions that do not participate in a reaction are called spectator ions and are not usually written in ionic equations.
Formulas that include only the particles that participate in reactions are called net ionic equations.
2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

20. MOLE TO MOLE
Reactions involving masses in grams of reactants and products can be achieved by converting grams into moles

21. LIMITING REACTANTS AND THEORETICAL YIELD
When a reaction goes to completion and there is no loss of product, then the amount produced is called the theoretical yield
Many times there is one reactant that is expensive so an excess of the other reactant is used, this ensures that all the expensive reactant is used. When the limiting reactant is used up the reaction stops.
Method to determine limiting reactant
Calculate the amount of product that would be formed if the first reactant was consumed
Repeat step 1 for second reactant