# Mass Percentages of Elements in a Compound

## Mass Percentages of Elements in a Compound

There are two ways to describe molecular structures for compounds, first; knowing how many atoms of each element involved in the composition of the compound and second; know percentages in terms of mass of elements in this structure, i.e., element in g 100 grams of the compound, the percentage can be found for each element in the composition of compound as follows:

1.      Find the molar mass of a compound of molecular form.

2.     Set and find the mass of each element in a molecule, i.e., product of atomic mass for each element x number of its atoms

3.     Find percentage for the item in the compound by the following relationship:

## Example 1

Calculate the percentage for each carbon, hydrogen and oxygen in the compound of isopentyl acetate (C7H14O2) (substance released by the bee insect).

Solution:

## Example 2

a) Find out mass percentages of elements in C2H2O4 acid.

b) What is the mass percentage of crystal water in C H O .2H O compound?

Solution:

## Example 3

Find out the mass of Ca in 20 g of Ca3(PO4)2.

Solution:

## Example 4

In 10 g of CuSO4.5H2O,

a) Find out mass of Cu.

b) Find out mass percentage of crystal water.

Solution: