Question

A sample of a compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen. What is the empirical formula of this compound

Answer 1

Answer:

The empirical formula is CH2O, and the molecular formula is some multiple of this

Explanation:

In 100 g of the unknown, there are 40.0⋅g12.011⋅g⋅mol−1 C;  6.7⋅g1.00794⋅g⋅mol−1 H; and  53.5⋅g16.00⋅g⋅mol−1 O.

We divide thru to get, C:H:O = 3.33:6.65:3.34. When we divide each elemental ratio by the LOWEST number, we get an empirical formula of CH2O, i.e. near enough to WHOLE numbers. Now the molecular formula is always a multiple of the empirical formula; i.e. (EF)n=MF.So 60.0⋅g⋅mol−1=n×(12.011+2×1.00794+16.00)g⋅mol−1.Clearly n=2, and the molecular formula is 2×(CH2O) = CxHyOz.