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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: chmdummy1982 on February 15, 2009, 05:33:07 PM

Title: Empirical Formula Problem
Post by: chmdummy1982 on February 15, 2009, 05:33:07 PM

Hi. I am trying to solve a couple of chemistry problems relating to using the empirical formula and am struggling with it. Can someone show me how they would do it.

Here they are:

A hydrocarbon mixture consists of 88.89% carbon and 11.11% hydrogen by mass. What is the empirical formula of the hydrocarbon?

If the molecular weight of the hydrocarbon is approximately 54 g/mol, what is the molecular formula?



Thanks!

Title: Re: Empirical Formula Problem
Post by: Astrokel on February 15, 2009, 06:08:03 PM

There are many online tutorials to this. Google: http://chemistry.about.com/od/workedchemistryproblems/a/empirical.htm

Title: Re: Empirical Formula Problem
Post by: Vidya on February 15, 2009, 11:45:47 PM

first take out % of oxygen.
Divide each % by its atomic mass to take out the mole ratio of each atom.get the smallest ratio and that will give you empirical formula.Try it.I have given you simple outline.Divide molar mass with empirical formula mass to get the number n
(Empirical formula)n  =  molecular formula

Title: Re: Empirical Formula Problem
Post by: Doom91 on February 16, 2009, 12:55:10 AM

the answer should be C4H6 and it should be butadiene

Title: Re: Empirical Formula Problem
Post by: Vidya on February 16, 2009, 02:08:28 AM

yes C4H6 is correct formula
But you can not be sure of it name ,it can be Butyne .So don't predict functional groups.