Question

A compound contain carbon, hydrogen and nitrogen in the ratio 18:2:7. Calculate the empirical formula? If molecular mass of the compound is 108g , what is the molecular formula?​

Answer 1

The Empirical formula and Molecular formula of the Compound are C3H4N and C6H8N2 respectively.

Given:-

The ratio of C, H2, and N2 = 18:2:7

Molar Mass of compound (mm) = 108g

To Find:-

The Empirical formula and Molecular formula of the Compound.

Solution:-

We can simply find the Empirical formula and Molecular formula of the Compound by using the following steps.

As

The ratio of Carbon = 18

The ratio of Hydrogen = 2

The ratio of Nitrogen = 7

Relative ratio = Ratio/Mass

Relative ratio of Carbon = 18/12 = 1.5 = 3

Relative ratio of Hydrogen = 2/1 = 2 = 4

Relative ratio of Nitrogen = 7/14 = 0.5 = 1

So, the Empirical formula of the compound = C3H4N

Molecular Mass of Compound (mm) = 108g

Empirical Mass of Compound (im) = 12*3 + 1*4 + 14

im = 36+4+14 = 54

n = empirical mass / molecular mass

$n = \frac{im}{mm}$

$n = \frac{108}{54}$

$n = 2$

Now,

The Molecular Formula = Empirical Formula *n

MF = (C3H4N)*2

MF = C6H8N2

Hence, The Empirical formula and Molecular formula of the Compound are C3H4N and C6H8N2 respectively.

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