CHEMISTRY 100 LECTURE Unit IV
PART 1 CHEMICAL REACTIONS A chemical reaction occurs when there is a change in chemical composition.
Reactions are represented by a balanced chemical equation.
2Al(s) + 3H2SO4(aq) -> Al2(SO4)3(aq) + 3H2(g)
The equation usually has number subscripts, state subscripts, coefficients, symbols, and an arrow.
Are these equations balanced?
I. Evidence of a reaction- One of the following would be observed: a. A precipitate is formed or dissolved
b. A change of color
c. Effervescence occurs (gas formation)
d. Energy in the form of heat, light, or electricity is released
II. Types of Chemical Reactions Know and complete A. Composition/Combination Reactions - One product is formed: 1. Metal + Nonmetal combines to form an Ionic compound ex.
combines to form 2. Metal Oxide + H2O a Base ex.
page 1 combines to form 3. Nonmetal Oxide + H2O an Acid ex.
B. Decomposition-A single reactant will form two or more products 2- decomposes 1. Carbonates (CO3 ) to oxides and CO2(g) Ex.
2- decomposes 2. Sulfites (SO3 ) to oxides and sulfur dioxide gas Ex.
3. Binary Ionic Compounds decomposes to Metal + Nonmetal
C. Combustion Reactions involves organic compounds:
General Form: (CxHyOz) + O2(g) CO2(g) + H2O(g)
page 2 D. Single Replacement Reactions An element reacts with a compound to form a different compound and a different element. The first element takes the place of the second element. Metals tend to replace metals and hydrogen, and nonmetals replace nonmetals. The element that does the replacing is said to be more active .
PREDICITING if the Single displacement reaction will occur USING: 1. Activity table for metals-for Single displacement types 1-->3 a. Which metals reacts with H2O
b. Which metals reacts with hot H2O, steam c. Which metals reacts with acids d. Which metals are more reactive 2. Activity series for halogens for single displacement type 4
Type 1. Metal + H2O Base + H2(g)
Type 2 Metal + Acid Salt + H2(g)
Type 3 Metal1 + Salt1 Metal2 + Salt2
Type 4 Nonmetal1 + Salt1 Nonmetal2 + Salt2
page 3 Examples
1. Zn(s) + H2O (g)
2. Hg(l) + HNO3(aq)
3. Ca(s) + HNO3(aq)
4. Cu(s) + AlBr3(aq)
5. Ag(s) + HCl(aq)
6. Ni(s) + AlCl3
7. Cl2 + KI(aq)
Use For: Single Replacement Reactions ONLY!!!
ACTIVITY SERIES FOR COMMON METALS MOST ACTIVE
K
Na Reacts with H2O(l)
Ca
Mg
Al Reacts with Acids to Mn Reacts with H2O(g), (Steam) liberate hydrogen gas Zn
page 4 Cr
Fe
Ni
Sn
Pb
H
Cu
Hg *Do not react with Acids to liberate hydrogen gas Ag
Pt
Au
LEAST ACTIVE *Note: Other types of rxns may occur with acids but will not produce H2 gas-you are not responsible to know these 'other' types
SOLUBILITY RULES FOR IONIC COMPOUNDS
Ion contained in Solubility Exceptions the Compound
Group IA soluble
NH4+ soluble
C2H3O2- soluble
NO3- soluble
Cl-,Br-, and I- soluble Ag+, Pb2+, Hg22+
SO42- soluble Ca2+,Sr2+,Ba2+,Pb2+
page 5 CO32-, PO43-, insoluble group IA and NH4+ CrO42-
S2- insoluble group IA,IIA, and NH4+
OH- insoluble group IA, Ca2+, Ba2+,Sr2+
STRONG BASES LiOH CsOH KOH Sr(OH)2 RbOH Ba(OH)2 NaOH Ca(OH)2
STRONG ACIDS HNO3 HCl HClO4 HBr H2SO4 HI
E. Double Replacement Reactions
1. In an double displacement (ion exchange) reaction, the positive end and negative end of compounds "change partners" to form new products:
a. Precipitate *Note: A ppt must form for the rxn to occur. (if it doesn't...Then NR!)
b. Less Ionized Substance.(Molecule formation) (1) Gas
page 6 (2) Neutralization
(3) A weak acid or weak base is formed
When there is no reaction:
Collision theory
Reaction Rate
Equilibrium
page 7