What is the Difference Between Mass Percent and Percent Composition?

The key difference between mass percent and percent composition lies in what they represent.

• Mass Percent: This refers to the percentage of a component in a mixture, expressed as a percentage of the total mass of the mixture. For example, if a compound has a total mass of 34.37 g, where 12.94 g is magnesium and 21.43 g is phosphorous, the mass percent of magnesium is 37.6% (12.94 g/34.37 g), and the mass percent of phosphorous is 62.4% (21.43 g/34.37 g).
• Percent Composition: This refers to the percentage of a particular chemical element in a mixture, expressed as a percentage of the total mass of the compound. For example, the percent composition of a water molecule is 20% hydrogen and 80% oxygen, as the mass of hydrogen is 11.2% (2 hydrogen atoms in a water molecule) and the mass of oxygen is 88.8% (1 oxygen atom in a water molecule).

In summary, mass percent gives the percentage of a component in a mixture, while percent composition gives the mass percentages of each chemical element in a mixture.

Comparative Table: Mass Percent vs Percent Composition

Mass percent and percent composition are two different concepts in chemistry. Here is a table highlighting the differences between them:

In summary, mass percent represents the percentage of an element's mass relative to the total mass of the compound, while percent composition represents the percentage of an element's mass relative to the molecular mass of the compound. Both concepts can be used to determine the amount of each element in a compound, but they take into account different parameters.