Question

A compound consisting of B, N, and H undergoes elemental analysis. The % composition by mass is found to be 40.28% B, 52.20% N, and 7.53% H. What is the empirical formula for this molecule? Enter in the empirical formula in the form BxNyHz

Answer 1

Empirical formula is the simplest ratio of components making up a compound.

The percentage composition of each element has been given

therefore the mass present of each element in 100 g of compound is

                      B                                   N                         H

mass          40.28 g                         52.20 g                 7.53 g

number of moles  

                 40.28 g / 11 g/mol      52.20 g / 14 g/mol    7.53 g / 1 g/mol

                = 3.662 mol                  = 3.729 mol             = 7.53 mol

divide the number of moles by the least number of moles, that is 3.662

                3.662 / 3.662              3.729 / 3.662              7.53 / 3.662

               = 1.000                           = 1.018                        = 2.056

the ratio of the elements after rounding off to the nearest whole number is

B : N : H = 1 : 1 : 2

therefore empirical formula for the compound is B₁N₁H₂          

that can be written as BNH₂