Daily Science feb
How many grams of CH4 is needed to produce
50.0 g CHCl3?
CH4 + 3Cl2  CHCl3 +3HCl
Lithium reacts spontaneously with bromine to
produce lithium bromide. Write the balanced
chemical equation for the reaction. If 25.0 g of
lithium and 25.0 g of bromine are present at the
beginning of the reaction, determine
the limiting reactant
the mass of lithium bromide produced
the mass of the excess
Percent Yield
pg. 85
Percent Yield
When you determine the amount of product
from a balanced chemical equation you are
finding the theoretical yield
rarely do scientists get the theoretical yield
in the lab, we measure the actual yield
need to know the efficiency-- determine
percent yield
Calculating percent
yield
percent yield= actual yield (from lab) /
theoretical yield (from calculations) x 100
expressed as a percent
Example
When potassium chromate (K2CrO4) is
added to a solution containing 0.500 g
silver nitrate, solid silver chromate (Ag2
CrO4) is formed.
determine the theoretical yield of the
silver chromate precipitate
if 0.455 g of silver chromate is obtained,
calculate the percent yield.
Practice Problems
Aluminum hydroxide is often present in
antacids to neutralize stomach acid (HCl).
If 14.0 g aluminum hydroxide is present in
an antacid tablet, determine the theoretical
yield of aluminum chloride produce when
the tablet reacts with stomach acid. If the
actual yield of aluminum chloride from this
tablet is 22.0 g, what is the percent yield?
Al(OH)3 +3HCl --> AlCl3 +3H2O