Percentage Composition

The percentage by mass of each element present in a compound is defined as Percentage Composition. It is calculated from the molecular formula by dividing the mass of a single element in one mole of a compound by the mass of one mole of that compound. The value is defined or expressed as a percentage.. 

Consider the chemical formula H2O, which stands for water

 Water contains two hydrogen molecules, and one mole of water weighs 18.0152 grams. 

One mole of hydrogen atom weighs 1.008 grams. 

As a result, 2 hydrogen moles weigh 2.016 grams. 

As a result, one mole of water has 2.016 grams of hydrogen. 

As a result, the hydrogen percentage composition would be 2.016/18.0152 = 11.19 percent. 

Let us now look more closely at percentage composition and its calculation:

Any compound’s percent composition is a statement of its composition in terms of all the components present. The chemical analysis reveals the relevance of this composition calculation.

Formula for Percentage Composition

Using the formula below, we can express the percentage composition of a particular element:

        % CE =gE / gT×100

where, % CE is the percentage composition of the element E. The numerator (gE) indicates how much of element E is present in the compound. Whereas the denominator (gT) is the total amount of all the elements present in that compound.

To get the percentage form of the composition this ratio is multiplied by 100

We multiply this ratio by 100 to acquire the composition’s percentage form

Percent Composition Formula Properties 

The formula of percent composition by mass is utilized in percent composition science. The formula % composition, also known as the formula for mass percentage, is calculated as a ratio of the quantity of each component contained in the compound to the total amount of the individual components of the compound multiplied by 100.

In layman’s words, the formula for an element’s mass percentage or percent composition by mass is as follows:

 (Mass of element / Molecular weight of compound) * 100 = Percent Composition by Mass 

The mass or weight of the components and the compound is typically measured in grammes. The above formula clearly shows that the percentage composition of a compound may be represented in terms of each of the individual components present in the complex.

The following equation is used to compute the proportion by mass of an element in given compound: 

percent CE = (gE/gT) * 100, 

where CE is merely a representation of an element’s percentage composition, 

gE is the total amount of element, and gT is the total weight of the compound. 

When the ratio is multiplied by 100, the percentage composition formula is obtained. The molecular formula can also be derived from the percent content of an element in a specific molecule. This is easily computed because it is the ratio of one element’s molecular weight to the compound’s molecular weight. As a result, the formula for mass percentage is also useful in getting the molecular formula, especially when the chemical formula of a newly found chemical compound is unknown.

Methods for estimating the % composition of components in a compound

1. Calculate the molar mass of each element in the compound in grams per mole.
2. Determine the total molecular mass of the molecule.

3.Divide the molar mass of the component by the total molecular mass.

4.You will now have a number ranging from 0 to 1.

5. Multiply it by 100% to get the percentage composition.

Example: Potassium Ferricyanide

Determine the mass percent composition of each element in a molecule of potassium ferricyanide, K3Fe(CN)6

How to Determine the Growth Rate or Percentage Change

Step 1: Determine each element’s atomic mass in the molecule.

The atomic mass of each element in the molecule must first be determined in order to calculate mass percent. K3Fe(CN)6 is a compound composed of potassium (K), iron (Fe), carbon (C), and nitrogen (N). Making use of the periodic table:

• K has an atomic mass of 39.10 g/mol.
• Fe has an atomic mass of 55.85 g/mol.
• C has an atomic mass of 12.01 g/mol while N has an atomic mass of 14.01 g/mol.

Step 2: Determine each element’s mass combination.

The second step is to calculate the total mass of each element’s combination. Each molecule of K3Fe(CN)6includes three K atoms, one Fe atom, six C atoms, and six N atoms. Multiply these figures by the atomic mass to find the mass contribution of each element.

K’s mass contribution is 3 x 39.10 = 117.30 g/mol.

Fe’s mass contribution = 1 x 55.85 = 55.85 g/mol

C’s mass contribution is 6 x 12.01 = 72.06 g/mol.

N’s mass contribution is 6 x 14.01 = 84.06 g/mol.

​ Step 3: Determine the molecule’s total molecular mass.

The molecular mass is the total of each element’s mass contributions. To obtain the total, simply add each mass contribution together.

K3Fe(CN)6 molecular mass = 117.30 g/mol + 55.85 g/mol + 72.06 g/mol + 84.06 g/mol

K3Fe(CN)6 has a molecular mass of 329.27 g/mol.

​

Step 4: Determine each element’s mass percent makeup.

To calculate an element’s mass percent composition, divide the element’s mass contribution by the total molecule mass. This figure must then be multiplied by 100% to be stated as a percentage.

For K, the mass percent composition of K is equal to the mass contribution of K/molecular mass of K3Fe(CN)6 multiplied by 100 percent.

K mass percent composition = 117.30 g/mol/329.27 g/mol x 100%

K mass percent composition = 0.3562 x 100%

K’s mass percent composition is 35.62 percent.

For Fe, the mass percent composition of Fe is equal to the mass contribution of Fe/molecular mass of K3Fe(CN)6 multiplied by 100 percent.

Fe mass percent composition = 55.85 g/mol/329.27 g/mol x 100%

Fe mass percent composition = 0.1696 x 100%

Fe content in mass percent = 16.96%

​​For  C:

C mass percent composition = C mass contribution/K3Fe(CN)6 x 100%

C mass percent composition = 72.06 g/mol/329.27 g/mol x 100%

C mass percent composition = 0.2188 x 100%

C’s mass percent composition is 21.88 percent.

For N, write:

N mass percent composition = N mass contribution/molecular mass of K3Fe(CN)6 multiplied by 100 percent

N mass percent composition = 84.06 g/mol/329.27 g/mol x 100%

N mass percent composition = 0.2553 x 100%

N has a mass percent composition of 25.53 percent.

​The Solution

K3Fe(CN)6 is composed of 35.62% potassium, 16.96% iron, 21.88% carbon, and 25.53% nitrogen.

Checking your work is usually a good idea. If you combine all of the mass percent components together, you should get 100 percent. 35.62 percent plus 16.96 percent plus 21.88 percent plus 25.53 percent equals 99.99 percent. What happened to the other.01 percent? This example shows the consequences of large figures and rounding mistakes. In this case, two significant numbers were utilised after the decimal point. This allows for an inaccuracy of around 0.01. The solution in this example falls within these parameters.