Percent Yield

Reaction is not always 100 % complete, there are several factors that the actual yield is not equal with theoretical yield.  Theoretical yield is the expected amount of product/s if all limiting reagent has been consumed, while actual yield is the amount of product/s obtained based from actual reaction. For example in making cookies, you are expecting 100 pcs of cookies but only 95 pcs are made.  Therefore the actual yield is 95 pcs and the theoretical is 100 pcs.  There are many factors that can affect why actual yield is not equal with the theoretical yield.

To determine if how efficient is the chemical reaction, percent yield can be calculated.  Percent yield is the proportion of the actual yield and the theoretical yield, as shown in the formula below:

Sample Problem:

Industrially, vanadium metal, which is used in steel alloys, can be obtained by reacting vanadium (V) oxide with calcium at high temperatures

In a process,  154 g of V2O5 reacts with enough  Ca.

a)  Calculate the theoretical yield of V.

b)  Calculate the percent yield if 83 g of V obtained.

Solution:

a.  Calculating theoretical yield 

b.  Percent yield

TRY THIS:

1.  Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere)  and in the production of  aluminum metal.  It is prepared by the reaction:

In one process, 600 g of CaF2 are treated with an excess of H2SO4.

a)  Calculate the amount of HF produced.

b)  Calculate the percent yield.

2.  When heated, lithium reacts with nitrogen to form lithium nitride. Write the balanced equation of this reaction and what is the theoretical yield of Li3N in g when 12.3 g of Li are heated with 33.6 g of N2?  If the actual yield of Li3N is 5.9 g, what is the percent yield of the reaction?