Question

Butane mol A sample of an alcohol is tested and found to contain 52% carbon, 35% oxygen, and 13% hydrogen by mass.

Tests indicate that the molecular weight of the molecule is between 30 and 80.
What is the molecular formula of the alcohol?

Answer 1

`C_(2)H_(6)O`

Step-by-step explanation:

For a compound as:

`C_(a)H_(b)O_(c)`

Let say your sample weighs 100 g, then you have

52 g of C

35 g of O

13 g of H

Now you need to calculate the moles in the sample:

moles of C = 52 / 12 = 4.3333

moles of O = 35 / 16 = 2.1875

moles of H = 13 / 1 = 13

Now you divide the moles by the least to have a proportion (2.1875):

moles of C = 4.3333 / 2.1875 = 2

moles of O = 2.1875 / 2.1875 = 1

moles of H = 13 / 2.1875 = 6

So the molecule proportion of atoms is C:H:O = 2:6:1

`C_(2x)H_(6x)O_(x)`

Now to find x you have to calculate the MM:

MM
`C_(2x)H_(6x)O_(x)` = 12 * 2x + 1 * 6x + 16 * x = 46x

For x = 1 => MM = 46(1) = 46

For x = 2 => MM = 46(2) = 92

Since the MM is between 30 and 80, x = 1

`C_(2)H_(6)O`