Mass Percent Calculations

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EMurphy_2L
Posts: 128
Joined: Sat Sep 07, 2019 12:16 am

Mass Percent Calculations

Postby EMurphy_2L » Thu Oct 10, 2019 5:50 pm

What is the mass percent of C7H15NO3?
How do you do this? I'm used to being given the amount of grams of a compound and its components to find mass percentage composition...

WesleyWu_1C
Posts: 117
Joined: Thu Jul 25, 2019 12:16 am

Re: Mass Percent Calculations

Postby WesleyWu_1C » Thu Oct 10, 2019 5:56 pm

It might be easier if you assume that there is only one molecule. You would first find the total mass of that molecule. Then you would find the mass of each element in that one molecule. So for example, since there are 7 moles carbon in one mole of that molecule, you would do 7 times the molar mass of carbon. Once you have the mass of each element in that molecule and the total mass of that molecule, then you divide each element's mass by the total mass of that molecule and multiply by 100%. Then you would get the mass percentage of each element in that compound (all the percentages should add up to 100%).

Daniel Toscano 1L
Posts: 95
Joined: Tue Nov 13, 2018 12:18 am

Re: Mass Percent Calculations

Postby Daniel Toscano 1L » Thu Oct 10, 2019 6:34 pm

Wesley explained it very well. Then, once you have the mass percentage of each element, you can do the rest of the problem normally.

Tiffany Chao 2H
Posts: 117
Joined: Fri Aug 09, 2019 12:17 am

Re: Mass Percent Calculations

Postby Tiffany Chao 2H » Thu Oct 10, 2019 7:27 pm

You should first find the molar mass of C7H15NO3 which is 161.199 g/mol. After that, find the mass percentage of each element in the molecule.

For carbon: (7 x 12.011 g/mol)/(161.199 g/mol) = 0.52157 x 100% = 52.157%

For hydrogen (15 x 1.008 g/mol)/(161.199 g/mol) = 0.09380 x 100% = 9.380%

Repeat the same for nitrogen and oxygen. It should add up to 100%.

Daniel Martinez 1k
Posts: 50
Joined: Wed Sep 18, 2019 12:16 am

Re: Mass Percent Calculations

Postby Daniel Martinez 1k » Thu Oct 10, 2019 7:43 pm

First, you would need to calculate the molar mass of C7H15NO3. After that, you have to find the molar masses of each element of that molecule. One needs to divide the molar masses of each element by the total molar mass of C7H15NO3 and multiply by 100% to find the mass percentage compositions.


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