Limiting Reactant
May 06, 2014
Limiting Reactants and Stoichiometry
limiting reactant-
excess reactants-
Identifying the Limiting Reactant
When
masses of reactants are provided and we do
not know which is in excess, we must first determine which one is the limiting
reactant
calculating how much product will be made.
Limiting Reactant
May 06, 2014
How to Identify the Limiting Reactant:
Step 1: Make sure you have a balanced chemical equation for the
reaction.
Step 2: Find the molar masses of both reactants.
Step 3: Convert the masses of the reactants into moles.
Step 4: Use mole ratios for each moles of the reactants to determine
the possible amount of product (so 2 mole ratios, one for each
reactant).
Step 5: The reactant that produces the least number of moles of
product is the LIMITING REACTANT!
Step 6:
Now use the MOLES of the LIMITING REACTANT to
determine the amount of product made from the reaction.
Limiting Reactant
May 06, 2014
Ex.
Hydrogen fluoride, (HF(g)), is a highly toxic gas. It is produced as
follows:
CaF2 (s) +
H2SO4(aq) -->
HF (g) +
CaSO4(s)
Determine the limiting reactant when 1.00 g of calcium fluoride
reacts with 15.5g of sulfuric acid.
Limiting Reactant
May 06, 2014
Stoichiometry Using the Limiting Reactant
After you have determined the limiting reactant, you use the mole of the
product from the moles of the limiting reactant to find the mass of the
product!
Ex. Zinc oxide, ZnO (s), is formed by the reaction of zinc sulfide, ZnS(s), and
oxygen gas.
ZnS(s) +
O2(g) -->
ZnO(s) +
SO2(g)
If 16.7 g of zinc sulfide reacts with 6.7 g of oxygen gas, what mass of zinc oxide
is produced?