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Jocelyn Martinez-1K
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Joined: Tue Nov 15, 2016 3:00 am


Postby Jocelyn Martinez-1K » Thu Oct 05, 2017 11:54 pm

Just need clarification on this problem, I understand that our mass percentage composition of C10H16O is 152.2264g. But I'm having a difficult time understanding why we divide 152.2264g to C, H, and O. ((ex) 120.1g x 100%/152.2264). Thanks!

Nishma Chakraborty 1J
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Re: F1

Postby Nishma Chakraborty 1J » Fri Oct 06, 2017 12:34 am

Hey! So based on the diagram, we interpret the molecular formula to be C10H16O (which has a molar mass of 152.228 g/mol). The question is asking for the mass percentage composition of each element in the molecular formula. That can be found by using this equation: (mass of element/total mass of compound)*100. So in the case of carbon, the mass of the element=12.01(carbon's molar mass)*10(number of carbons present in molecular formula)=120.1g/mol and the total mass of the compound would be 152.228 g/mol. When plugged into the formula ((120.1 g/mol divided by 152.228)*100), you get 78.9% Carbon. So basically in the compound, carbon comprises 78.9% of the total mass. You just follow the same steps for the other two elements. Hoped this helps!

Karen Ung 2H
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Re: F1

Postby Karen Ung 2H » Fri Oct 06, 2017 9:30 am

We divide the mass of C, H, and O by 152.228g/mol in order to find the mass percent composition of each element. If there are 10 carbons in the formula, you would multiply 12.01*10 in order to find the total mass of carbon, which is 120.1g. Then divide by the total mass of the molecule to find the amount of carbons in the molecule represented by a percentage.

Guangyu Li 2J
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Re: F1

Postby Guangyu Li 2J » Fri Oct 06, 2017 5:53 pm

1. Taking the Carbon as example, the relative atomic mass of Carbon is approximately 12.01. Since there are 10 Carbon atoms, you need to multiply 12.01 by 10 when you calculate the mass of carbon. Then you divide this result by the total mass which is 152.2264 and you will get the corresponding mass composition percentage.
2. Percentage of C: (12.01*10)/152.2264=78.90%
Percentage of H: (1.0079*16)/152.2264=10.59%
Percentage of O: (16.00*1)/152.2264=10.51%

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