Question

An analysis of nicotine (MW = 162 g/mol)
gives 74.0% carbon, 8.65% hydrogen, and
17.3% nitrogen. What is the TRUE
(MOLECULAR) formula for nicotine?

All I need are the formulas!!

Answer 1

Note this doesn't add to 100% but I'll assume it does. I don't think that will change the formula.
Take 100 g sample to give you
74.0 g C
8.65 g H
17.3 g N

Convert to mols.
74/12 = ?
8.65/1 = ?
17.3/14 = ?
Find the ratio of these numbers with the smallest being 1.00. The easy way to do that is to divide the smallest number by itself (which automatically gives you 1.00), then divide the other two numbers by the smallest number. This gives you the empirical formula.
Then determine the weight of the empirical formula.
molecular formula = (CxHyNz)_n.
Your job then is to determine n. Here is how you get that.
(162/empirical formula) = ? and round to a whole number.

Answer 2

C10H14N2