If CH3 has a molar mass of 30.0g in a compound what is the molecular formula?

Question

it's the molec. mass (30)/ Mass of empircal 15.04) after I divided that I got 1.995, and rounded it to two. But what do I do with the two? Do I mulitiply it by CH3 to get C2H6?? I'm confused.

Answer 1

You're right. The empirical formula is (CH3)x. The molar mass of (CH3)x is:

(12 + 3*1)x = 15x

So:

15x = 30, x = 2

And the molecular formula is:

C2H6 (CH3-CH3 : ethane)

Answer 2

yes, you round to 2 and get C2H6, assuming CH3 was the empirical formula, which I think it was