7.3 & 7.4 LIMITING REAGENT
REACTANTS
PRODUCTS
REACTANTS
PRODUCTS
LIMITING REAGENT
 In most chemical reactions, one of the reactants is usually used up before the other.
The chemical that is used up first LIMITS how much product can be formed.
 Limiting Reagent /Reactant - The reactant that is completely used up first.
When this runs out, the reaction stops.
 Excess Reagent/Reactant – Reactant(s) that is/are left over after the reaction is
complete.
 The amount of all products in a chemical reaction is determined by the amount of
limiting reagent!
STEPS YOU SHOULD FOLLOW!
1. Write a BaLaNcEd Chemical Equation!
2. Calculate moles of products IF not given!
3. Determine the limiting and excess
reagent by comparing the ratios from
the balanced chemical equation!
4. Convert moles of product to mass of
product using limiting reagent value!
LIMITING REAGENT
Example 1: Limiting Reagent Problems Involving Amounts (moles)
 Determine the amount of titanium metal produced when 2.8 mol of titanium (IV)
chloride reacts with 5.4 mol of magnesium
LIMITING REAGENT
Example 2: Limiting Reagent Problems Involving Masses
 Methanol (CH3OH) can be made using a synthesis reaction involving carbon monoxide
and hydrogen.
a. What mass of methanol can be produced from 9.80 g of carbon monoxide and 1.30 g of
hydrogen?
b. What mass of excess reagent remains?
LIMITING REAGENT
 How many grams of hydrogen gas would be produced if 50g of aluminum is
reacted with 250g of sulfuric acid in a displacement reaction?
Page 332 # 1-4, Page 334 # 1-3, page 335 #1-11