Chapter 11: stoichiometrySection 4 : Percent yield

Objectives Calculate the theoretical yield of a chemical reaction from data. Determine the percent yield for a

chemical reaction

limiting reactant &Excess reactant( in your own words )

limiting reactant: is the reactant that limits the extent of the reaction and determines the amount of the product formed. Excess reactantsReactants that leftover when a reaction stops

Theoretical and Actual YieldsThe theoretical yield

is the maximum amount of product that can be produced

from a given amount of reactant.

A chemical reaction rarely produces the theoretical yield of

product.A chemist determines the actual yield of a reaction through a

careful experiment in which the mass of the product is measured

The actual yield

is the amount of product produced when the chemical reaction is carried out in an experiment.

Percent yield is a measure of the efficiency of a Percent yield

The actual yield Chemists need to know how efficient a

reaction is in producing the desired product. One way of measuring efficiency is by means of percent yield.

Percent yield of product: Percent yield of product: is the ratio of the actual yield to the

theoretical yield expressed as a percent

Answer the following: What is the theoretical yield of NaCl when

20 grams of Cl2 reacting with excess of sodium iodide

a. Balance the equation: NaI(aq) Cl2(g) NaCl(aq) I2(s).

If the actual yield of NaCl is find the percent yield ?

Percent Yield in the Marketplace : Percent yield is important in the cost

effectiveness of many industrial manufacturing processes.

For example, the sulfur is used to make sulfuric acid ( H 2 S O 4 ). Sulfuric acid is an important chemical because it is a raw material used to make products such as

fertilizers detergentsPigments textiles

Formulas for polyatomic ionic compounds:

The cost of sulfuric acid affects the cost of many of

the consumer items you use every day.

The first two steps in the manufacturing process are

shown below.

The first step, the combustion of sulfur, produces an almost

100% yield.

The second step also produces a high yield if a catalyst is

used at the

relatively low temperature of 400°C.

A catalyst : is a substance that speeds a reaction but does not

appear in the chemical equation.