Could someone help me to understand this chemistry question?

Question

This question is just a 1 or 2 word answer, and I'm confused whether it's a trick question or not.

Which type of formula, empirical or molecular, can be obtained from elemental analysis that gives percent composition?

I saw an example in my textbook that shown me how to get the empirical formula from the percent composition, and from that answer, it was able to obtain the molecular formula. So what's the answer? It says "or" in the question, but then again, it might be a trick question.

Oh ok, I forgot that the example in the textbook gave the molar mass. My bad, sorry guys.

Answer 1

the answer is both... u first find the empirical formula and then you use that to calculate the molecular formula

Answer 2

it's empirical formula

your textbook probably then showed how, using the empirical formula and the molar mass of the stuff, you can determine molecular formula. Percent composition, for example, for carbon will tell you the mass ratio of the whole molecule and the carbon.

for instance empirical formula may be CH4
and the percent composition of hydrogen is 25 %
but if the formula/molecular mass is found to be 32 then the molecular formula is C2H8

you could have been told that there was 25% H and 75% C; you would then just say there are 25g of H and 75g C, use their molar masses to find their molar ratio in the particular molecule; for instance 25/1= 25 mol H and 75/12 = 6.25 molC meaning H : C is 4 : 1 so CH4

hope that helped

Answer 3

You can get the empirical formula with the elemental analysis. If you know the molar mass of the molecule (mass spectroscopy) you can determine the molecular formula from the two methods.

Answer 4

Empirical because percent composition does not tell you anything about the molecular weight, which is required to determine the molecular formula.

Answer 5

it seems straightforward. you can only reliably get the empirical formula from elemental analysis, so that would be the answer to this question. sometimes you may have other information that allows you to deduce the molecular formula though.