Consider a compound that is 40.00% C, 6.71% H, and 53.28% O by mass. Assume that we have a 100 g sample of this compound. What are the subscripts in the empirical formula for this compound?

Question

Consider a compound that is 40.00% C, 6.71% H, and 53.28% O by mass. Assume that we have a 100 g sample of this compound. What are the subscripts in the empirical formula for this compound?

Answer 1

When given % composition, you can assume 100 g of material and then the % is equal to grams.

40.00 g C x 1 mol C /12 g = 3.33 moles C

6.71 g H x 1 mol H / 1 g = 6.71 moles H

53.28 g O x 1 mol O / 16 g = 3.33 moles O

Mole ration of C : H : O = 1 : 2 : Empirical formulal = CH₂O