Percent Composition

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Isabelle Fontanilla 1I
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Percent Composition

Postby Isabelle Fontanilla 1I » Thu Oct 04, 2018 12:31 am

What will you have to do if the mass percent of the different elements that make up a compound/molecule does not add up to 100%? Like, for example, if the percent composition is, like, 41% C, 25% O, and 22% H. 41+25+22≠100.

Also, is it alright to assume that a 99.96% composition is close enough to 100% that I can treat is as 100%?

Ania Chavez Dis 4D
Posts: 14
Joined: Fri Sep 28, 2018 12:27 am

Re: Percent Composition

Postby Ania Chavez Dis 4D » Thu Oct 04, 2018 12:46 am

Mass percentage composition is found by calculating a fraction of the total mass by each element present in a compound. The whole compound itself would would equal 1 or 100% and all the elements that make it up would only be a fraction, so it will always have to add up to 100%. Try checking if you are missing any elements or maybe reference the problem so that I can help you.

As for the 99.96%, there must have been an error while calculating the problem (probably rounding too much?) that caused the percentage to be less, but it most likely would still be right as long as you recheck your work.

Max Kwon 1J
Posts: 40
Joined: Fri Sep 28, 2018 12:18 am
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Re: Percent Composition

Postby Max Kwon 1J » Thu Oct 11, 2018 12:01 am

I am pretty sure it is miniscule enough to count as 100%, so the calculation shouldn't change much. However, if it doesn't add up you should look at the reaction and see what could be lost, like oxygen in oxygen gas.

Maria Solis Disc 1G
Posts: 63
Joined: Fri Sep 28, 2018 12:27 am
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Re: Percent Composition

Postby Maria Solis Disc 1G » Mon Oct 15, 2018 2:27 am

When I was doing one of these questions myself the number wasn't adding up to 100%. Although significant figures may have caused you to get to 99% you can try truncating all your answers to see if you get 100%, if you rounded all your answers.


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