Homework Help: chemistry

Posted by jhong on Tuesday, March 13, 2012 at 6:39pm.

A 12.0g sample of carbohydrate contain 4.50g of carbon, 3.25g of oxygen, and some hydrogen. Determine the percent by mass of hydrogen in your product.

Find the empirical formula for a compound that consists of aluminum and chlorine in which the aluminum is 20.2 % by mass.

. A sample contains 71.65% CL, 24.27% C and 4.07% H. the molecular weight is known to be 98.96 g/mol. What are the empirical and molecular formulas?

chemistry - DrBob222, Tuesday, March 13, 2012 at 7:57pm
I worked 1 and 2 for you a couple of days ago.
g H(atoms that is) = 12.0-gO - gC = ?
%H = (g H/12.O)*100 = ?

20.2% Al
100-20.2 = %Cl
Take a 100 g sample which will give you
20.2g Al
79.8 g Cl
Convert grams t mols. mol = grams/molar mass.
Then find the ratio of Al and Cl to each other with the smallest number being 1.00. That will give you the empirical formula.

#3. This done the same way as #2.
Post your work if you get stuck.

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