Question

Nicotine contains 74.0% C and 8.7% H and 17.3% N and has a mass of 162.1 grams
What's the molecular formula?

Answer 1

first find the ratio of the atoms in the molecule by dividing each percentage by the ralative atomic mass of the element
eg C = 74 / 12

Answer 2

H = 8.7 / 1.008
N = 17.3 / 14.007

Answer 3

divide each of the results by the smallest to give values very close to whole numbers
You will then have the ratio of the elements in the whole numbers.

Answer 4

THis is the empirical formula for nicotine
Add up the atomic masses to get the molecular mass
Compare this with the ginen mass 162.1
From this you get the molecullar formula.