Question

An organic compound contains C=40%,H=6.6%,O=53.4%,if the vapour density of the compound is 15, find its empricial formula and molecular formula?
please answer in detail solution.

Answer 1

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.