Question fee2e

Jan 21, 2014

Percent error and percent yield are not related chemically, but the mathematical calculations are similar.

PERCENT ERROR

Percent error expresses as a percentage the difference between an experimental value and an accepted or theoretical value.

% error =

|accepted value - experimental value|/accepted value × 100 %

EXAMPLE

In an experiment, you calculate the density of a block of aluminum to be 2.72 g/cm³. The density of aluminum is actually 2.70 g/cm³. Calculate the percent error of your measurement.

Solution

% error =

|accepted value - experimental value|/accepted value × 100 % =

(|2.70 g – 2.72g|)/(2.70 g)# × 100 % = $\frac{| - 0.02 |}{2.70}$ × 100 % = $\frac{0.02}{2.70}$ × 100 % = 0.7 %

PERCENT YIELD

Percent yield expresses the actual yield of a product as a percentage of the theoretical yield.

% yield = actual yield/theoretical yield × 100 %

Example:

In an experiment, you obtained 0.650 g of Cu. The theoretical yield of Cu is 0.745 g. What was your percent yield?

Solution

% yield = theoretical yield/actual yield × 100 % = $\frac{0.650 g}{0.745 g}$ × 100 % = 87.2 %