Tuesday, February 8, 2011

Limiting Reactants

 Limiting Reactant Strategy

If a problem mentions amounts of more than one reactant, its probably a limiting reactant problem.

  1. Go from each reactant to amount of product (grams of each reactant to grams of product)
  2. The reactant that produces the lower amount of predicted product is the limiting reactant.  This amount of product is also the amount that can be produced.
  3. The other reactant is your excess reactant.

For Example:

Fe + S  √†  FeS

If I have 28g of Iron (56 g/mol) and 24g of Sulfur (32 g/mol), how much FeS can be made and what is the limiting reactant?

28 g Fe  x  1 mol Fe  x  1 mol FeS  x  87.92g FeS  =  44 g FeS
                 55.85 g Fe     1 mol Fe       1 mol FeS

24 g S  x  1 mol S  x  1 mol FeS  x  87.92g FeS  =  66 g FeS
                32.07 g S     1 mol S         1 mol FeS

Fe is the Limiting reactant because it runs out first and produces less FeS.

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