Ravela Da Cruz


Percent Composition Study Guide

Chemical compounds' atomic makeup can be expressed in several ways, including molecular formulae and percent composition.


We all know the importance of drinking water in our day-to-day lives. Remaining hydrated 💧 throughout the day is extremely important for the normal functioning of all the body organs and systems. It is because water constitutes approximately 60% of our bodies! This water content can also be stated as: the percentage composition of water in the human body is 60%. You might be wondering what a percentage composition is. Let's find out.

Percent Composition Source


The ratio of every element's amount to the overall amount of available components contained in the compound multiplied by 100 is the percent makeup. The amount is expressed in the grams of the various components present.

Any compound's percentage composition reflects its makeup in the perspective of all of the components present. As a result, it aids in the chemical examination of a particular substance.

% mass = (mass of element in 1 mole of the compound) / (molar mass of the compound) x 100%



Many commercialized products contain the bicarbonate of soda (sodium hydrogen carbonate), and NaHCO3 is the formulation. Let's now calculate the mass percent of Na, H, C, and O in sodium hydrogen carbonate. To begin, use the Periodic Table to seek up the atomic weight of the elements. The masses of the atoms are discovered to be:

  • Na - 23
  • H - 1
  • C - 12
  • O - 16

Next, calculate how many grams of every element seem to be in a mole of NaHCO₃:

  • 23 g (1 mol) of Na
  • 1 g (1 mol) of H
  • 12 g (1 mol) of C

48.00 g (3 mole x 16 gram per mole) of O 1 mole of NaHCO₃ has the following mass: 23g + 1g +12g + 48 g = 84 g

And the elemental mass percentages become

  • % Mass of Na = 23 g / 84 g x 100 = 27.36 %
  • % Mass of H = 1 g / 84 g x 100 = 1.20 %
  • % Mass of C = 12 g / 84 g x 100 = 14.30 %
  • % Mass of O = 48 g / 84 g x 100 = 57.14 %


You may determine the percentage composition of a compound experimentally, and you could use all these data to calculate a compound's empirical formula. Any compound's percentage composition reflects its makeup in the perspective of all of the components present.


1. What does percentage composition depend on?

By dividing the mass of every element by the compound's entire mass, the compound's percent composition (by weight) may be derived.

2. What is percent composition? Why is it important in chemistry?

A compound's percentage composition is essential since it helps us figure out what percentage of every element constitutes that complex. In nature, everything is chemically or physically bonded with other elements. To figure out how much of a substance is in a sample, you must first figure out the proportion of the specimen.

3. Does percent composition change in a compound?

Considering that a compound is pure, the percentage composition of that compound will always be the same.

4. In what other ways can you apply percentage composition?

Comparing the percentage composition achieved practically to the theoretical value estimated from the compound's formulation can determine the purity of a chemical. Air quality and fuel combustion can all be constituted from the percentage makeup.

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  1. Percent Composition. https://www.ck12.org/c/chemistry/percent-composition/lesson/Percent-Composition-CHEM/. Accessed 18 Feb 2022.
  2. How to Calculate Mass Percent Composition. https://www.thoughtco.com/mass-percent-composition-example-609567. Accessed 18 Feb 2012.
  3. Percent Composition of Compounds. https://courses.lumenlearning.com/introchem/chapter/percent-composition-of-compounds/#:~:text=Percent%20composition%20is%20calculated%20from,is%20presented%20as%20a%20percentage. Accessed 18 Feb 2022.