Mole to Mole Conversion

• Coefficients in balanced equations tell us the number of moles reacted or produced
• They can also be used as conversion factors
• What you need over what you have

3x + Y ---> 2Z 

Stoichiometry

• Stoichiometry is a branch of chemistry that deals with the quantitative analysis of chemical reactions.
• It is a generalization of a mole conversion to chemical reactions.
• understanding the 6 types of chemical reactions is the foundation of stoichiometry

Synthesis

• A+B-->AB
• Usually  elements ---> compounds

Ex: Na2O + H2O ---> 2NaOH

Decomposition

• AB ---> A + B
• Reverse of synthesis 

Ex; CaCO3 ---> CaO + CO2

Single Replacement

• A + BC ---> B + AC 

Ex:  Fe + CUSO4 ---> Cu + FeSO4

Double Replacement

• AB + CD ---> AD + BC
• Metals always go first

 Ex: FeCl3 + 3NaOH ---> 3NaCl + Fe(OH)3

Neutralization

• Reaction Between an acid and a base

Ex: NaOH + HCl ---> NaCl + H2O

Combustion

• Reaction of something (usually hydrocarbon) with air
• Hydrocarbon combustion always produces CO2 and H2O

Ex:  2C4H10 + 13O2 ---> 8CO2 +10H2O

Empirical Formulas and Molecular Formulas

Empirical formulas are the simplest formula of a compound that show only the simplest ratios.
   -Not the actual atoms


   Ex: - The empirical formula for Hydrogen gas is H
         - Dinitrogen TetraOxide is not N2O4 in an empirical formula format. It is NO2.


Molecular formulas give the actual number of atoms.


We need to know the ratio of each element to determine the empirical formula.


This table will help to determine the ratio for an element.


Atom     Mass     Molar Mass     Moles              Smallest Mole     Ratio
  C          8.4g           12.0g            0.7/0.35      =       2                  2
  H          2.1g           1.0g              2.1/0.35      =       6                  6
  O          5.6g           16.0g            0.35/0.35    =       1                  1


The simplest ratio could be decimals.
For certain decimals you may need to multiply everything by a common number.


Decimal                                            Multiplying Coefficient 
0.5                                                                   2
0.33/0.66                                                         3
0.25/0.75                                                         4 
0.2, 0.4, 0.6, 0.8                                              5


Atom     Mass     Molar Mass     Moles              Smallest Mole     Ratio
  C         50.5g         12.0g          4.21/3.16   =         1.32 x 3           4
  H         5.26g           1.0g          5.26/3.16   =         1.66 x 3           5
  N         44.2g         14.0g          3.16/3.16   =         1      x 3           3


To find the molecular formula you need the molar mass. If you know the empirical formula.


Empirical                      Molecular
C2H6O                              ?
     ?                              138g/mol


12.0(2)+1.0(6)+16.0=  46.0g/mol


Empirical                       Molecular
C2H6O                               ?
46.0g/mol                      138g/mol


138.0/46.0= 3   (C2H6O)3


Empirical                        Molecular
C2H6O                         C6H18O3
46.0g/mol                      138.0g/mol

Percent Composition

The percentage by mass of an element in a compound is always the same.


To find the percent by mass determine the mass of each element present in one mole.


   Example: Hydrogen in Water (H20)


                  H=2.0g O=16.0g  18.0g/mol        2.0 / 18.0 = 0.111
                                                                                      = 11.1%


                  Sodium in Salt (NaCl)


                  Na=23.0g Cl=35.5g 58.5g/mol    23.0 / 58.5 = 0.393
                                                                                         = 39.3%