Question

The empirical formula for carbohydrates is CH2O. The molecular weight for a particular carbohydrate is 90.09 grams. What is the molecular formula for that carbohydrate? (atomic masses: C =12.0107; H = 1.00794; O = 15.9994)

Answer 1

We find the weight of the empirical formula:
12.0107 + 2 x 1.00794 + 15.9994
= 30.03

Now, we divide the molecular weight by the weight of the empirical formula to find the number of times the empirical formula repeats:
90.09 / 30.03
= 3

The formula is 3(CH₂O)
C₃H₆O₃