3. Chemical Reactions
Molecular Formula
Struggling with General Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first video
Video duration:
2mRelated Videos
Related Practice
Skip to main content
Recall that the molecular formula gives the actual number of different elements in a given compound. Meaning, it gives us the real formula for the compound. The empirical formula on the other hand just gives us the relative number of those different elements in that same compound. Up to this point, we've learned to calculate the empirical formula when given either the masses or the percentages of those elements within that compound. But how exactly would we determine the molecular formula for those same compounds? Well, here we have a chart. And in this chart, we're talking about 3 compounds, glucose, octane and salicylic acid. We're gonna say that their empirical formulas are given as CH2 o. Remember that there are subscripts of 1 and 1 there. We have c 4h9 and c 7h603. In order to determine their molecular formulas, we can use n factors. N factors are just numbers that we can multiply the empirical formula by in order to determine the molecular formula. So for example, glucose has an n factor of 6. That means I will multiply each of the subscripts of the empirical formula by 6, and that'll give me my molecular formula. So that'd be 6 carbons, 12 hydrogens, and 6 oxygens. So the molecular formula of glucose is c 6 81206. Octane, it has an n factor of 2. So multiplying those subscripts gives me c 8 h 18. And then finally, salicylic acid has a n factor of 1, which means that the molecular formula and empirical formula are the same. So just remember, when you're given the n factor, just multiply the empirical formula by it, and you'll determine what your molecular formula will be. But what happens when we don't have the n factor? How do we determine it? In the next series of videos, we'll go through the different steps required to find the different n factors for any given compound once you've determined its empirical formula.
6:53
