A compound contains 24.27% C, 4.07% H and 71.65% Cl. The molar mass is about 99g.

What is the molecular formula ?

Molecular formula = C₂H₄Cl₂

Explanation:

Molecular formula:

Molecular formula consist of symbols of elements present in compound with numbers of atoms of each element in subscript.

Empirical formula:

It is the simplest formula gives the ratio of atoms of different elements in small whole number .

Given data:

Percentage of hydrogen = 4.07%

Percentage of Cl = 71.65%

Percentage of carbon = 24.27%

Molar mass = 99 g/mol

Molecular formula = ?

Solution:

Number of gram atoms of H = 4.07 / 1.01 = 4.0

Number of gram atoms of Cl = 71.65 / 35.5 = 2.0

Number of gram atoms of C = 24.27 / 12 = 2.0

Atomic ratio:

           H              :          C             :         Cl

          4/2            :        2/2            :       2/2

           2               :          1             :        1

C : H : Cl = 1 : 2 : 1

Empirical formula is CH₂Cl.

Molecular formula:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

Empirical formula mass  = 12+1×2+ 35.5 = 49.5

n =  99/49.5

n = 2

Molecular formula = n (empirical formula)

Molecular formula = 2 ( CH₂Cl)

Molecular formula = C₂H₄Cl₂