Molecular Formula Quiz#1 Question

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Molecular Formula Quiz#1 Question

Postby 704578485 » Tue Oct 13, 2015 8:53 pm

On the self prep quiz #1 I am having trouble with question 9. I calculated that within a 100g sample of the unknown compound you get 3.283moles Carbon, 3.286moles Oxygen, and 7.817moles Hydrogen. When I divide all those values by the smallest number of moles(3.283) I do not get a whole number for 7.817/3.283 and the number for the number I get i am having a hard time converting it to a simple fraction. Where am I going wrong?

Sparks55 3F
Posts: 18
Joined: Fri Sep 25, 2015 3:00 am

Re: Molecular Formula Quiz#1 Question

Postby Sparks55 3F » Tue Oct 13, 2015 9:28 pm

At that point in the problem, you just need to round it out to the nearest integer.
Usually the answer will be extremely close to an integer, for example 5.11 or 7.89. However, I think a decent rule of thumb is that when the answer is , or a multiple of or , then multiply the whole answer by 2 or 3 respectively in order to get all of the molar ratio numbers to be integers.

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