This document discusses stoichiometric calculations and concepts like limiting reactants, theoretical yield, and percent yield. It explains that the coefficients in a balanced chemical equation give the ratio of moles of reactants and products. It also describes how to use the molar ratios to calculate the mass of a product formed or reactant used from the mass of another substance. Sample stoichiometry problems are provided that involve calculating moles or masses of substances. The concepts of limiting reactant, theoretical yield, and percent yield are defined.
2. Stoichiometric Calculations
From the mass of
Substance A you can
use the ratio of the
coefficients of A and B
to calculate the mass of
Substance B formed (if
it’s a product) or used
(if it’s a reactant)
3. Stoichiometric Calculations
Starting with 1.00 g of C6H12O6…
we calculate the moles of C6H12O6…
use the coefficients to find the moles of H2O…
and then turn the moles of water to grams
C6H12O6 + 6 O2 6 CO2 + 6 H2O
4. Sample #1
• CH4 +2O2 2H2O + CO2
How many moles of CH4 are needed to make 13
moles of water?
5. Sample #2
• CH4 +2O2 2H2O + CO2
• How many moles of water are made from 10g
of Oxygen?
6. Sample #3
CH4 +2O2 2H2O + CO2
• How many grams of water are produced from
100 moles of CH4?
7. Sample #4
CH4 +2O2 2H2O + CO2
• How many grams of Oxygen are needed in
order to produce 200 g of carbon dioxide?
9. Limiting Reactants
• The limiting reactant is the reactant present in the
smallest stoichiometric amount
– In other words, it’s the reactant you’ll run out of first (in
this case, the H2)
11. Theoretical Yield
• The theoretical yield is the amount of product
that can be made
– In other words it’s the amount of product possible
as calculated through the stoichiometry problem
• This is different from the actual yield, the
amount one actually produces and measures
12. Percent Yield
A comparison of the amount actually
obtained to the amount it was possible to
make
Actual Yield
Theoretical Yield
Percent Yield = x 100
