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May 6, 2016

Homework Help: chemistry

Posted by Lucy J. on Wednesday, February 10, 2010 at 12:18am.

you are given samples of two pure compounds, one of which is a gas and one of which is a liquid at room temperature. by elemental analysis, both compounds are found to have the following composition (by mass):
52% C
13% H
35% O

(a) Determine the empirical formula of both compounds.
(b) The molar mass of both compounds is determined to be 46.0g/mol. Name one method for calculating the molar mass of a pure gas and one method for calculating the molar mass of a pure liquid.
• chemistry - DrBob222, Wednesday, February 10, 2010 at 12:41am

Take a 100 g sample which will give you
52 g C
13 g H
25 g O

Convert each to moles.
52/12.01 = ??
13/1.008 = ??
35/16 = ??
Now you want to find the whole number ratios of these values. The easiest way to do that is to divide the smallest number by itself. That assures you of getting 1.00000 for that number. Then divide the other numbers by the same small number and round all to whole numbers. That will give you the empirical formula.
You can estimate the molar mass of a liquid by using the ebullioscopic method (boiling point elevation method). For a gas one can use the Victor Meyer method.

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