1. 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

2. Percent Yield
pg. 85

3. 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

4. Calculating percent yield
percent yield= actual yield (from lab) / theoretical yield (from calculations) x 100
expressed as a percent

5. Example
When potassium chromate (K2CrO4) is added to a solution containing g silver nitrate, solid silver chromate (Ag2 CrO4) is formed.
determine the theoretical yield of the silver chromate precipitate
if g of silver chromate is obtained, calculate the percent yield.

6. 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