Chemistry ocr a empirical formula question

benzene is a compund made of hydrogen and carbonwith relativemolecular mass of 78
92.2% carbon 7.8% hydrogen
what is the molecular formula
ocr a level chemistry question help

Reply 1

TSR Jessica

Sorry you've not had any responses about this. :frown:

Are you sure you’ve posted in the right place? Posting in the specific Study Help forum should help get responses. :redface:

I'm going to quote in Tank Girl now so she can move your thread to the right place if it's needed. :h:

Spoiler

Reply 2

Psraim

Original post by youreanutter

benzene is a compund made of hydrogen and carbonwith relativemolecular mass of 78
92.2% carbon 7.8% hydrogen
what is the molecular formula
ocr a level chemistry question help

92.2/12 = 7.683
7.8/1 = 7.8

7.8/7.683 = 1.02 which is literally just 1, so there's one Carbon atom and one Hydrogen atom in the Empirical Formula. Giving the Relative formula mass of he Empirical Formula as 13 (12+1). To get the Molecular Formula divide the Relative Molecular Mass of the molecule by the Relative formula mass of the Empirical Formula, 78/13 = 6. This means there are six times as many atoms than in the Empirical Formula. So Benzene is C1x6 H1x6 = C6H6.

Reply 3

lucaknows

Bit late but here you go:92.2 / 12 (12 being Mr of carbon)=7.6837.8 / 1 (1 being Mr of hydrogen)= 7.87.8 / 7.683 = 1.015Answer is basically 1 so Carbon and hydrogen is 1:1 ratio or CH is empirical formula.CH Mr = 13 However Molecular formula Mr = 7878 / 13 = 6Therefore answer is C6H6 because you multiply empirical formula by 6