Percent Composition Cartoon

Updated: 7/23/2020

This storyboard was created with StoryboardThat.com

By Viraj Sharma

- One day Mike was wondering how to calculate percent composition by mass. He decided to ask his science teacher after school to help him
- Mr. Obert, I was wondering if you could teach me how to calculate percent compositions?
- Of course! Let me give you a lesson on percent composition!
- Awesome! Thanks!
- .
- Let's look at the whiteboard here. Remember that the molar mass represents 100% of the mass of 1 mole of a substance
- I have written the formula on the board for calculating percent compositions. It's completely fine if you don't understand it the first time
- mass % = mass x 100%
- ______________
- Total mass
- _________________ __________
- Next, we find the molar mass for the entire compound, so we look up the molar mass for oxygen, which is 16.000g and when added with hydrogen, the total molar mass is 18.016 g. To determine the percent of Hydrogen in water, simply divide the molar mass of hydrogen by the total molar mass of water and multiply by 100%. So, hydrogen makes up 11.19 percent of water
- We first look at hydrogen on the periodic table. The molar mass for hydrogen is 1.008g. However there are 2 atoms of hydrogen, so the total molar mass is 2.016.
- .
- To calculate the % composition, we calculate the percentages of each element in the compound by mass
- Sure! Let's start with an easy and common example, water
- %H: mass of H x 100% = 2.016 x 100% = 11.19 %
- Total molar mass 18.016
- Oh that makes sense! Can you show an example?
- .
- Also one important thing to remember, the percentages should always add up to 100, and thats a good way to check your work!
- To find the percentage of oxygen in water, you repeat the process again - use the molar mass of oxygen and divide it by the total molar mass of water and multiply by 100%. So, oxygen makes up 88.81 percent of water.
- ________________ _____________
- %O: mass of O x 100% = 16.000 x 100% = 88.91 %
- Total molar mass 18.016
- Yeah, go for it!
- Okay I understand now, can I try to solve a problem?