Question

8. Determine the molecular formula of the following compound: 40.3% B, 52.2% N.
7.5% H, and a molar mass of 80 g/mol. (5 marks)

Answer 1

Answer:

Molecular formula = B₃N₃H ₆

Explanation:

Given data:

Percentage of B = 40.3%

Percentage of N = 52.2%

Percentage of H = 7.5%

Molar mass = 80g/mol

Molecular formula = ?

Solution:

Number of gram atoms of B = 40.3/ 10.8= 3.73

Number of gram atoms of N = 52.2/ 14 = 3.73

Number of gram atoms of H = 7.5 / 1 = 7.5

Atomic ratio:

  B              :            N                  :      H

3.73/3.73    :         3.73/3.73        :      7.5/3.73

     1            :            1                    :         2

B : N : H = 1 : 1 : 2

Empirical formula is  BNH ₂

Molecular formula:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

n = 80 g/mol/ 26.8 g/mol

n = 3

Molecular formula = n (empirical formula)

Molecular formula = 3 (BNH ₂)

Molecular formula = B₃N₃H ₆