Mass Percent

Mass Percent is the percentage of a particular element within a compound. 

Atomic Mass Vs. Molecular Mass

Concept: Understanding the difference between Atomic Mass & Molecular Mass

1m

In order to find the atomic mass of an element you must look it up on your periodic table. 

Example: What is the total mass of each of the following elements?

a. Sodium                                              b. Gold                                                 c.  Mercury 

2m

The total mass of a compound is the sum of each elemental atomic mass. 

Example: What is the total mass of each of the following compounds?

a. N2O5                                                            b. C12H22O11                                        c.  (NH4)3PO4

4m

Examining Mass Percent

Example: What is the percentage of carbon in sodium hydrogen carbonate, NaHCO3?

3m

In order to calculate the molecular mass or weight of a compound you must look up the atomic mass or weight of each element. 

Example: A sample of toothpaste contains tin (II), SnF2. Analysis of a 5.25 g sample contains 8.77 x 10-3 g of F. What is the percentage of tin (II) fluoride in the sample? 

5m

To go from the atomic mass of an element to the molecular mass of a compound you must use stoichiometric relationships. 

Problem: Hemoglobin contains 0.33% iron and has a molecular weight of 68 kg. How many iron atoms are in each molecule of hemoglobin?

6m