# whats the empirical formula

Discussion in 'DAT Discussions' started by dentalstudent2021, Jul 31, 2015.

1. ### dentalstudent2021

if 4.58% H , 40.9% C and 54.52% O is given

Molecular Mass is 264 g /ml

KBB does it a certain way but they don't round their calculations but do exact calculations which seems a tall task w/o a calc.

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3. ### RuffDay 2+ Year Member

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This is how I would do it.
First we know that oxygen takes about half of the weight of the total mass. I would round the Oxygen to 50%, but remember since we are under estimating, then we should round to a higher whole number.

50% of the molecular mass is 132g and divide that by the oxygen mass (16g) would be 8.25. Since we are underestimating, we round the oxygen to the higher whole number, 9.

With 120g left after subtracting the molecular weight of oxygen. We have about 80% of carbon. This is also an underestimate, so we have to round the whole number up or increase it by 1. 120g x .8 is about 96, then divide by 12g = 8 carbons. Since this is an underestimate, we want it to be a 9.

We now have C9O9 and the rest would be hydrogen. I am guessing it is C9H12O9.

The DAT won't be this hard.

4. ### BeaverLover SDN Gold Donor Gold DonorClassifieds Approved 2+ Year Member

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Did ADA list empirical formulas as being possible subject on DAT? Don't remember Chad going over it

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