Empirical Formula

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hannahtweedy
Posts: 29
Joined: Tue Nov 21, 2017 3:00 am

Empirical Formula

Postby hannahtweedy » Wed Apr 11, 2018 5:31 pm

Polyethylene is a hydrocarbon polymer used to produce food-storage bags and many other flexible plastic items. A combustion analysis of a 0.00126-g sample of polyethylene yields 0.00394-g of CO2 and 0.00161-g of H20. What is the empirical formula of polyethylene?

I've balanced the equation but now I'm just a bit confused on what to do next

ErinKim1I
Posts: 31
Joined: Fri Apr 06, 2018 11:03 am

Re: Empirical Formula

Postby ErinKim1I » Wed Apr 11, 2018 7:49 pm

Once you balanced the equation, just find % mass of each element, convert mass to mol, divide each element's # moles by the smallest # mol,make sure you get whole numbers or otherwise multiply to get a whole number, and the numbers you get are the ratios for the empirical formula.

hannahtweedy
Posts: 29
Joined: Tue Nov 21, 2017 3:00 am

Re: Empirical Formula

Postby hannahtweedy » Wed Apr 11, 2018 9:11 pm

More specifically, how would I find the mass percentages given a full balanced equation

Alicia Beebe
Posts: 37
Joined: Fri Apr 06, 2018 11:01 am

Re: Empirical Formula

Postby Alicia Beebe » Fri Apr 13, 2018 12:44 am

What I did is found the equation, and then I found out the moles of each of the products produced, using the given masses. From that, I found the number of atoms of carbon and hydrogen that were produced by looking at the molar ratios and the definition of a mole. Once I knew the quantity (in atoms) of each of those, I could look at the ratio and determine the empirical formula since each of those hydrogen and carbon atoms came from the polyethylene. I'm sure there are several ways, but this is the way that made most sense to me!


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