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Percentage Composition – Definition, Formula, Examples

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  • Last Updated : 28 Jun, 2022

Different constituent elements make up any chemical compound. In some chemical reaction calculations, you’ll need to figure out how much of a certain element is in a specific compound. Or, in order to understand the contribution of a specific element in any of the stoichiometric calculations of a chemical compound in which the element is present, the amount of the element in the molecule must be known. This can be determined by using the percent composition formula to get the element’s percentage composition in a particular compound.

Any compound’s percent composition expresses its composition in terms of all of the elements present. As a result, it helps in the chemical characterization of a particular compound.

What is Percentage Composition?

The percentage composition of any given compound is defined as the ratio of the amount of each element to the total amount of all individual elements that are available in the given compound and then multiplied by 100. 

In this, we measure the quantity of the elements in terms of grams which is present in the solution. This calculation is mostly used in the chemical analysis of the compound.

Formula Percentage Composition 

We can express the percentage composition of a given element using the formula below:

%CE = (gE/gT)×100

where 

  • % CE is the percentage composition of element E. 
  • gE is the total amount of element E present in the compound T.
  • gT is the total amount of all the elements present in the compound T.

Mass Percentage (w/w)%

To describe the concentration of an element in a compound or a component in a combination, we utilize the idea of mass percentage composition. The total percent by mass of each element contained in a compound is denoted by this term.

It’s important to note that the mass percentage composition can be calculated by dividing the mass of a component by the total mass of the combination. After that, multiply the ratio by 100. The mass percent (w/w)% is another name for it.

It’s important to note that the mass percentage composition can be calculated by dividing the mass of a component by the total mass of the combination. After that, multiply the ratio by 100. The mass percent (w/w)% is another name for it.

Sample Questions

Question 1: Calculate the percent composition of each element in water.

Solution:

The chemical formula of water is H2O. It contains 2 mole of Hydrogen and 1 mole of oxygen.

1 mole of Oxygen has molar mass of 16 g/mole.

1 × 16= 16 grams.

1 mole of Hydrogen has molar mass of 1.0108 g/mol.

1.008× 2 = 2.016 grams.

Total molar mass of H2O = 16+2.016 = 18.016 g/mol.

Formula of percentage composition,

%CE = (gE/gT)×100

Percentage composition of Hydrogen = (2.0016/18.016 )*100 = 11.19%

Percentage composition of oxygen = (16/18.016)*100 = 88.81%

Therefore, the percentage composition of hydrogen is 11.19% and oxygen is 88.81%.

Question 2: Calculate the Percentage composition of Carbon and Oxygen present in Glucose.

Solution:

The chemical formula of Glucose is C6H12O6.It contains 6 molecules of carbon, 12 molecules of hydrogen and 6 molecules of oxygen.

1  mole of carbon has molar mass of 12.01grams.

6 × 12.01= 72.06 grams.

1 mole of hydrogen has molar mass of 1.008 grams.

12 × 1.008 = 12.096 grams.

1 mole of oxygen has molar mass of 16grams.

6 × 16= 96 grams

Total molar mass of glucose = 72.06+12.096+96 = 180.16 g/mol.

Formula of percentage composition,

%CE = (gE/gT) × 100

Percentage composition of Carbon =(72.06/180.16) ×100 = 40%

Percentage composition of oxygen = (96/180.16) × 100 = 53.29%

Therefore, the percentage composition of carbon is 40% and oxygen is 53.29%.

Question 3: Calculate the percentage composition of all elements present in Calcium Hydroxide.

Solution:

The chemical formula of Calcium Hydroxide is Ca(OH)2.It contains 1 molecules of calcium, 2 molecules of hydrogen and 2 molecules of oxygen.

1  mole of calcium has molar mass of 40.01grams

1 × 40.01= 40.01 grams.

1 mole of hydrogen has molar mass of 1.008 grams.

2 × 1.008 = 2.016 grams.

1 mole of oxygen has molar mass of 16grams.

2 × 16= 32 grams.

Total molar mass of Calcium Hydroxide = 40.01+2.0016+32 = 74.102 g/mol.

Formula of Percentage composition,

%CE = (gE/gT)×100

Percentage composition of Calcium =(40.01/74.102)×100 = 54.12%

Percentage composition of oxygen  = (32/74.102) × 100 = 43.2%

Percentage composition of hydrogen  = (2.0016/74.102) × 100= 2.7%

Therefore, the percentage composition of calcium is 54.12%, oxygen is 43.2% and hydrogen is 2.7%.

Question 4: Calculate the percentage composition of nitrogen present in nitric acid.

Solution:

The chemical formula of nitric acid  is HNO3. It contains 1 molecules of hydrogen, 1 molecules of nitrogen and 3 molecules of oxygen.

1 mole of hydrogen has molar mass of 1.008 grams.

1 × 1.008 = 1.008 grams.

1  mole of nitrogen has molar mass of 14.01grams.

1 × 1401= 14.01 grams.

1 mole of oxygen has molar mass of 16 grams

3 × 16= 48grams.

Total molar mass of nitric acid = 14.01+1.008+48 = 63.02 g/mol.

Formula of percentage composition,

%CE = (gE/gT)×100

Percentage composition of nitrogen =(14.01/63.02) ×100 = 22.23%.

Therefore, the percentage composition of nitrogen is 22.23%.

Question 5: Calculate the Percentage composition of potassium present in potassium permanganate .

Solution:

The chemical formula of potassium permanganate is KMnO4. It contains 1 molecules of hydrogen, 1 molecules of nitrogen and 3 molecules of oxygen.

1 mole of hydrogen has molar mass of 1.008 grams.

1 × 1.008 = 1.008 grams.

1  mole of nitrogen has molar mass of 14.01grams

1 × 14.01= 14.01 grams.

1 mole of oxygen has molar mass of 16grams.

3 × 16= 48grams.

Total molar mass of nitric acid = 14.01+1.008+48 = 63.02 g/mol.

Formula of percentage composition,

%CE = (gE/gT)×100

Percentage composition of nitrogen =(14.01/63.02) × 100 = 22.23%

Therefore, the percentage composition of nitrogen is 22.23%.

Question 6: Calculate the Percentage composition of Chlorine present in Hydrochloric acid.

Solution:

The chemical formula of Hydrochloric acid  is HCl. It contains 1 molecules of hydrogen and 1 molecules of chlorine.

1 mole of hydrogen has molar mass of 1.008 grams.

1 × 1.008 = 1.008 grams.

1  mole of chlorine has molar mass of 35.45 grams.

1 × 35.45 = 35.45 grams.

Total molar mass of hydrochloric acid = 1.008+35.45 = 36.458 g/mol.

Formula of Percentage composition,

%CE = (gE/gT)×100

Percentage composition of chlorine = (35.45/36.458)×100 = 97.23%

Therefore, the percentage composition of chlorine is 97.23%.

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