The compound methyl butanoate smells like apples. Its percent composition is 58.8% C, 9.9% H, and 31.4% O. What's the empirical formula?

To find the empirical formula you would first need to find the moles of each element:

58.8g / 12.0g = 4.9 mol C

9.9g / 1.0g = 9.9 mol H

31.4g / 16.0g = 1.96 O

Then you divide by the smallest number of moles of each:

4.9/1.96 = 2.5

9.9/1.96 = 6

1.96/1.96 = 1

Since there is 2.5, you find the least number that makes each moles a whole number which is 2.

So the empirical formula is C5H12O2.