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Topic: Help w/ empirical formula Q.  (Read 4142 times)

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Offline AzMa1

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Help w/ empirical formula Q.
« on: July 20, 2007, 03:41:53 PM »
The Question: Polystyrene can be prepared by heating styrene with tribromobenzoyl peroxide in the absence of air. A sample prepared by this method has the empirical formula Br3C6H3(C8H8)n, where the value of n can vary from sample to sample. If one sample has 10.46% Br, what is the value of n.

I know the answer is 19 but I have no clue how they got that. The "C6H3" part confuses me. I don't know how to find n with something like that.
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I have no teacher right now so I really appreciate your help. Only two more chapters to go.

Offline Borek

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Re: Help w/ empirical formula Q.
« Reply #1 on: July 20, 2007, 04:43:11 PM »
Try to express Br % (using molar masses) as a function of n. For example if the formula of some compound is H(CH2)nBr molar mass is 1+n*14+80 and Br% = 80/(1+n*14+80)*100%. Then solve for n.
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