a level chemistry

Analysis of a compound alcohol, X, showed that it contained 52.14% carbon, and
13.13% hydrogen by mass (hint: the remainder would be oxygen). Mass spectrometry gave
a molecular ion of m/z = 46.
(i) Deduce the empirical formula of X.
(ii) What is the molecular formula of X?
how do you answer these

Reply 1

huriya666

So for these questions, it is very systematic.
As they have told you it is an alcohol, you know there is oxygen as well.
100-52.14-13.13= 34.73%
Next just remove the percentage sign and replace it with grams.
So theoretically, there are 52.14g of carbon, 13.13g of hydrogen and 34.73g of oxygen
Then work out the number of moles of each.
Carbon: 52.14/12= 4.345
Hydrogen 13.13/1= 13.13
Oxygen: 34.73/16= 2.170625
Then divide each number of mole by the smallest number to get a ratio, in this case it would 2.170625
Carbon: 4.345/2.170625= 2.00172...
Hydrogen 13.13/2.170625= 6.04...
The ratio of carbon to hydrogen to oxygen is 2:6:1
Therefore the empirical formula is C2H6O
The molar mass of C2H6O is 46
As this is equal to the m/z value, the molecular formula is also C2H6O.
I hope this helped!