Question

A compound contains carbon, hydrogen, and nitrogen as its only elements. A 9.353 g sample of the compound contains 5.217 g of carbon and 1.095 g of hydrogen; the remainder is nitrogen. What is the empirical formula for the compound?

Answer 1

Let's have first the atomic weights of these elements which are:

C = 12 g/mol; H = 1 g/mol; N = 14 g/mol

Let's determine the mass of N:

mN = 9.353 - 5.217 - 1.095 = 3.041 g

Now let's determine the empirical formula:

C = 5.217 / 12 = 0.4348

H = 1.095 / 1 = 1.095

N = 3.041 / 14 = 0.2172

Dividing all between 0.2172 (cause is the lower one):

C = 0.4348 / 0.2172 = 2

H = 1.095 / 0.2172 = 5

N = 0.2172 / 0.2172 = 1

These numbers represents the number of atoms of these elements in the empirical formula so:

EF = C₂H₅N

Hope this helps