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Empirical and molecular formula help


Chemstryandbio

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Hi I know most of you are worried with EE and TOK but I would appreciate it if you could help me out:

 

The question: Which compound's molecular formula is the same as its empirical formula:

 

A. C2H5OH

B. CH3CHOOH

C. C6H6

D. C8H18

 

I know its obviously not C or D, empirical formulae: CH and C4H9 but I dont know for the first two please help...

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The empirical formula is the lowest whole number ratio of atoms in a compound.

In A, there is 2 C atoms, 6 H atoms and 1 O atom. This is already the lowest whole number ratio of atoms (if you divided the formula by 2, you would get half an O atom which is not a whole number). So this is the molecular formula and the empirical formula.

In B, there are 2 C atoms, 4 H atoms and 2 O atoms. This can be divided by 2 to give CH2O, which is the lowest whole number ratio of atoms in the compound ( by the way there is mistake in the formula, it should be CH3COOH).

Edited by Msj Chem
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