Stoichiometry (cont.)

Stoichiometry calculations allow us to find how much of chemical #1 is involved in a chemical reaction based on the amount of chemical #2

* Mole conversion is back!!
* always know which you want to reduce and reduce it correctly

Here are some examples of Stroichiometry involving particles, moles, gas volume and mass

Eg.
The combustion of propane, C3H8, proceeds according to the following equation
              C3H8 + 5O2 --> 3CO2 + 4H2O
a) what mass of CO2 is produced by reacting 2.00 mol of O2?
    mass of CO2 can be calculated by :
     1) convert moles of O2 to moles of CO2
     2) convert moles of CO2 to mass of CO2
     the equation will be:
      mass of CO2 = 2,00 mol O2 x 3 mol CO2 x 44.0 g CO2 = 52.8 g
                                                      5 mol O2       1 mol CO2       
     * don't forget to check the sig. fig
b) If a sample of propane is burned what mass of H2O is produced if the reaction also     produces 50.0 L of CO2 @ STP?
    steps to do this question are
    1) convert the given data 50.0 L to numbers of mol is STP
    2) convert mol of CO2 to mol of H2O
    3) convert mol H2O to mass
    4) check for the units and sig. fig.
    equation will be:
   mass of H2O = 50.0L CO2 x 1 mol CO2 x 4 mol H2O x 18.0 g H2O = 53.6g
                                                 22.4L CO2   3 mol CO2    1 mol H2O
c) 1.35E-6 g of C3H8 is extracted.  How many molecules of CO2 are produced if the gas   sample is burned with enough O2
   Steps to get the answer
   1) convert the mass of C3H8 to mol
   2) using mol ratio to convert the mol of C3H8 to mol of CO2
   3) convert mol of CO2 to numbers of molecules
   4) chech the unit and numbers of sig. fig
   Equation:
   # of CO2 molecules = 1.35 g C3H8 x 1 mol C3H8 x 3 mol CO2   x 6.022E22
                                                              44.0g C3H8    1 mol C3H8    1 mol CO2
                                   = 5.54E16 molecules