Mass Percent Converted to Grams

Moderators: Chem_Mod, Chem_Admin

Margia Adriano 2A
Posts: 94
Joined: Wed Sep 30, 2020 10:00 pm

Mass Percent Converted to Grams

Postby Margia Adriano 2A » Mon Oct 12, 2020 12:25 pm

Hi! I think this might have been answered already, but I am still a little confused about it. When doing mass percent composition, why is that we turn the percentages into grams out of 100 grams. For example, a sample that is 64.7% C would be turned into 64.7 grams in order to turn it into moles? Why do we do this even if we are given a mass for the actual sample? Thank you!

Akash J 1J
Posts: 103
Joined: Wed Sep 30, 2020 9:58 pm
Been upvoted: 1 time

Re: Mass Percent Converted to Grams

Postby Akash J 1J » Mon Oct 12, 2020 12:28 pm

Hi! There is no reason other than the ease of thinking in terms of 100g. That way it is easier to see the numbers add up to 100g instead of adding up to the given mass of the sample compound.
After converting the mass percentages to grams that add up to 100g, when you convert to moles then divide by the smallest number, the ratio of moles will be no different than if you used the actual masses of each element in the given sample compound.

Keeryth Sandhu 1H
Posts: 97
Joined: Wed Sep 30, 2020 10:04 pm

Re: Mass Percent Converted to Grams

Postby Keeryth Sandhu 1H » Mon Oct 12, 2020 12:38 pm

Hi! It just makes it easier to think about in terms of 100g, especially after calculating the mass percent composition.

Melis Kasaba 2B
Posts: 91
Joined: Wed Sep 30, 2020 9:49 pm

Re: Mass Percent Converted to Grams

Postby Melis Kasaba 2B » Mon Oct 12, 2020 1:04 pm

It helps you easily turn the mass percentages into grams because it's the same number. When you turn these grams into moles, it'll give you the same answer as if you had used the masses for the actual sample because the ratio is the same. But the problem can be more convenient and easier to visualize if you use mass percentages and it can help you catch math errors because you can easily check if it adds up to 100% or 100g.

Elizabeth Kaplan 3I
Posts: 119
Joined: Wed Sep 30, 2020 9:32 pm

Re: Mass Percent Converted to Grams

Postby Elizabeth Kaplan 3I » Mon Oct 12, 2020 5:28 pm

Hi! Just to clarify, you only need to turn the percentages of each given element into grams when you are determining an empirical or molecular formula. When you are doing mass percent composition, you simply divide the given grams of each element by the total molar mass of the compound and multiply by 100%. When determining an empirical or molecular formula, you turn the percentages of each given element into grams out of 100 grams because it is the easiest way to covert from decimal to percent so that you do not have to perform any extra calculations.


Return to “Empirical & Molecular Formulas”

Who is online

Users browsing this forum: No registered users and 1 guest