Download Percent Yield and Limiting Reactants

Percent Yield
and Limiting
Reactants
Using Reaction
Stoichiometry
Percent Yield
%
Yield= Actual Yield / Theoretical Yield x 100

Actual Yield- from a lab (what was actually
produced)

Theoretical Yield- from a reaction stoichiometry
problem (mathematical value… what you
should have gotten)
Percent Yield Practice
PbS + O2  PbO + SO2



Balance the equation above.
What is the theoretical yield of PbO if 200.0g of PbS is
reacted?
If 170.0g of PbO is obtained in a chemical reaction,
what is the percent yield?
More practice…

Upon heating, solid calcium carbonate
decomposes to form solid calcium oxide and
carbon dioxide gas.
 Write the complete balanced chemical
reaction for the reaction.

Determine the percent yield if 235.0g of calcium
carbonate is heated and 97.5g of carbon
dioxide is collected.
Limiting Reactants
 Limiting
Reactant- the reactant (reagent)
that produces the fewest moles of
product.
 Reaction can only form the amount of
product “allowed” by the limiting
reactant.
Limiting Reactant Steps




Balance the Equation
Use mole ratios to find the moles of a product
formed by each reactant (using the amounts
given in the problem)
The reactant that makes the smallest number of
moles of product is the limiting reactant. The other
is the excess reactant.
The smallest number of moles produced will be the
actual amount of product formed in the reaction.
To find excess reactant remaining:
 Subtract the two amounts of product formed
(from step #2 above) and use mole ratios convert
back to the reactant.
Limiting Reactant Practice
H 2 + O 2 → H 2O
 If 12.2 mol H2 and 8.4 mol O2 react…
 What is the limiting reactant/reagent? The
excess reactant?
 How
many moles of water are produced?
 How
many grams of water are produced?
 How
many moles of excess reactant
remain?