Instructional Video
Khan Academy

Khan Academy: Chemistry: Molecular and Empirical Formulas

9th - 10th
A video lecture explaining how to find the molecular and empirical formula knowing the percent composition of each element. The problem is solved in easy to follow steps. [9:30]
Instructional Video
Khan Academy

Khan Academy: Organic Chemistry: Spectroscopy: Proton Nmr: Hydrogen Deficiency Index

9th - 10th
How to relate molecular structure with the molecular formula using the hydrogen deficiency index (or number of degrees of unsaturation). [8:50]