Question

What is the empirical formula of a substance with 74.0% C , 8.65% H, and 17.4% N?

Answer 1

`C_5H_7N`

Explanation:

First, assume that there is 100 g of substance.

Next is to calculate the number of moles or each element:

`74.0 g C * (1mol C )/ (12.01 g) ~~ 6.16 mol C`
`8.65 g H * (1mol H )/ (1.008 g) ~~ 8.58 mol H`
`17.4 g N * (1mol N )/ (14.01 g) ~~ 1.24 mol N`

After getting the mol of each element, you can calculate now the mole ratio. Do this by dividing each number of moles by the lowest number of moles obtained.

`C= (6.16/1.24)~~ 5`
`H= (8.58/1.24)~~ 7`
`N= (1.24/1.24)~~ 1`

Therefore, the empirical formula of a substance with 74.0% C , 8.65% H, and 17.4% N is `C_5H_7N`