Excess and Limiting

A: Excess Quantity
   -A balanced equation describes what should happen in a chemical reaction
    Sometimes necessary to add more of one reactant than the equation
   
    -One reactant is the Excess quantity and some of it will be left over,the second   of reactant is used up to -----limiting Quantity
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Example:
How many grams of OCl2 will be formed when 44.0g of O2 react with 97.0g of Fl2?
Step1: balance the equation
             2Cl2+O2--->2OCl2
Step2: convert both reactants to the desired product 
             44g  mol O2 x 2molOCl2      x    87g =       239g OCl2
             32g                 1mol O2        1mol OCl2


            97.0gmol Cl2 x 2mol OCl2 x       87g         =119gOCl2
            71g                    2Cl2           1mol OCl2


According to the answer, Cl2 is limiting reactant and O2 is excess reactant 
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