Mass percentage- Definition and calculations

Published by Daniel Ozori on

Mass percentage– Definition

Mass percentage is a method used to represent the concentration of an element in a compound or a component in a mixture. The mass of 1 mole of a compound is the sum of all the masses of the moles of its component elements.

Mass percentage is calculated as the mass of a component divided by the total of the mixture, multiplied by 100%, We can calculate the percentage by mass of a component element of a compound from its formula.

Mass percentage– Calculations

Example: Calculate the percentage mass of nitrogen in Trioxonitrate (v) acid (HNO3). ( H= 1 , N=14 , O=16)


The molecular formula of Trioxonitrate (v) acid is HNO3 and in one mole of HNO3 there is 1 of Hydrogen, 1 mole of Nitrogen, and 3 moles of Oxygen.

So the collective molar masses of all the given elements in grams is given as ;

(1 × 1 + 1 × 14 + 1 × 16) = 63g

63g of HNO3 contains 14g of Nitrogen

We can therefore calculate the percentage by mass of nitrogen in HNO3

= 14 / 63 × 100% = 22.2%

Now let’s try a more difficult example;

Calculate the mass percent of silver in AgCl.


Now if you’re not familiar with the periodic table and it’s elements, this question is going to be a real brain knocker for you because the atomic masses weren’t given making it even harder.

Ag is the chemical symbol for silver ( the 47th element on the periodic table ) which has an atomic  mass of 107.87

And Cl is the chemical symbol for chlorine ( the 17th element on the periodic table ) and has an atomic mass of 35.453

Now that we have their atomic masses we can go on to calculating it.

(1 × 107.87 for silver) + ( 1× 35.453 for chlorine )


107.87 / 143.23 × 100%


So the mass percent of silver in AgCl is 75.31%

Fun fact; If you exposed a glass of water to space, it would rather boil rather than freeze


Anonymous · October 28, 2019 at 9:04 pm

Can you please explain atoms?

    Daniel Ozori · October 28, 2019 at 9:53 pm

    An article explaining what atoms are has already been published, please refresh your feeds to see it

Tips on studying chemistry | Easy Chemistry · December 17, 2019 at 12:42 pm

[…] what was taught in class, also practice the essential equations in chemistry like Molecular mass, Mass percentage, and Mole  and this should be done […]

Leave a Reply

Your email address will not be published.