1. Chemical Calculations
Lesson # 6 – Limiting & Excess Reagents

2. Definitions
In most chemical reactions, only one of the reactants is completely consumed. This reactant is known as the limiting reagent. Any reactant which is not completely used in is present in excess. The limiting reagent limits the amount of product which can be formed in a reaction.

3. Example 1
14 g of iron and 12 g of sulfur are available for reaction to produce iron (III) sulfide. What is the limiting reagent in the reaction?
Fe S → Fe2S3

4. Example 2
50.0 g of sulfur dioxide and 15.0 g of oxygen, plus an unlimited quantity of water react to form sulfuric acid. What is the limiting reagent, and what mass of sulfuric acid can be produced?
SO O H2O → H2SO4

5. Example 3
How many grams of carbon dioxide will be produced when 8.5 g of methane react with 15.9 g of oxygen?
CH O2 → CO H2O