Calculating percentage Composition
Calculate the percentage composition of magnesium carbonate, MgCO3
Mg = 24.31 + C = 12.01 + O3 =3(16.00) = 84.32
Mg = 24.31/84.32 x 100 = 28.83%
Formulas
Empirical formula
The lowest whole number ratio of atoms in a compound
Molecular formula
The true number of atoms of each element in the formula of a compound
Formulas for molecular compounds might be empirical – H2O can’t be reduced anymore but is the true amount of atoms
Determination Process
Assume 100g
Change everything to moles
Divide by the smallest value
Multiply to get whole number
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid? What are three uses for it?
C6H10O4, make nylon, food and medicine
Reactant –Left of equation, goes into the reaction
Product – right of the equation, finished reaction
Subscript – # of atoms
Coefficient – # of molecules
All matter and energy must be conserved
Chemical Equation Symbols
A) → indicates what is being made
B) ↔ reversible
C) + ∆ H heat added
D) - ∆ H heat lost
E) (s) solid
F) (l) liquid
G) (aq) aqueous, h2o added
H) (g) gas
Evidence of chemical reaction
Heat or light
Production of gas
Color change
Formation of a precipitant
Balancing chemical equations

Oxidation Reduction
Involves transfer of electrons
Transfer of electrons produces energy electrochemistry, batteries
Common process in synthesis. Single replacement reactions
Oxidation numbers used to indicate distribution and movement of electrons
1. Uncombined elements in a reaction have a zero oxidation