Question

A compound contains 4.07% Hydrogen, 24.27% Carbon and 71.65% of Chlorine. Its molar mass Is 98.96G. What are its empirical and molecular formulas?

Answer 1

Step 1: Given

A compound contains:

Hydrogen —$4.07\%$

Carbon$–24.27\%$

Chlorine$—71.65\%$

Molar Mass Is $98.96G$

Step 2: Evaluating Empirical Formulae

For each atom empirical formula is derived, by first, dividing the given percentages of atoms by their molecular masses.

Hydrogen — $4.07/1=4.07$

Carbon– $24.27/12=2.02$

Chlorine—$71.65/35.5=2.01$

Now divide all the values with the lowest obtained value.

Hydrogen — $4.07/2.01=2$

Carbon–$2.02/2.01=1$

Chlorine— $2.01/2.01=1$

Therefore, the empirical formula is ${\mathrm{CH}}_2\mathrm{Cl}$

Step 3: Calculation of Molecular Formulae

From empirical formula

${\mathrm{CH}}_2\mathrm{Cl}$

$$\begin{gathered} =12+2\times 1+35.5 \\ =49.5 \end{gathered}$$

The molecular weight- $98.96$ is double of empirical weight.

Therefore molecular formula is ${\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{Cl}}_2$.