Homework Help: Chemistry

Posted by Natalie on Friday, December 30, 2011 at 11:07am.

1) A compound has the following percentages by mass: barium, 58.84%; sulfur, 13.74%; oxygen, 27.43%. Determine the empirical formula of the compound.

2) If a 1.271-g sample of aluminum metal is heated on a chlorine gas atmosphere, the mass of aluminum chloride produced is 6.280 g. Calculate the empirical formula of aluminum chloride.

I don't understand these at all, could you at least help explain them/push me in the right direction on how to accomplish these?

Chemistry - DrBob222, Friday, December 30, 2011 at 2:15pm
Take a 100 g sample. That gives you
58.84 g Ba
13.74 g S
27.43 g O

Convert to moles. moles = grams/molar mass.

Then you want to find the ratio of the moles to each other with the smallest number being 1.00 (round if necessary but don't round too much). The easy way to do that is to divide the smallest number by itself; then divide all of the other numbers by the same small number.

For #2.
............Al + Cl2 = AlxCly
..........1.271........6.28
So you know Cl2 must be 6.28-l.271 = 5009g.
Then just follow the steps in problem 1.
Post your work if you have trouble.
Chemistry - wyatt, Monday, October 1, 2012 at 12:01am
6.256

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