Question

A hydrocarbon P contains $14.3 %$ hydrogen.

(i) Find out its empirical formula.

(ii) The relative molecular mass of it is $28$ . Calculate its molecular formula.

(iii) Name the organic compound P.

(iv) Write the structural formula of P.

Accepted Answer

The hydrocarbon P contains $14.3 %$ hydrogen. The percentage of carbon in the compound is $(100 - 14.3) = 85.7 %$ .

The ratio of carbon and hydrogen can be calculated as follows:

Elements Percentage composition Atomic mass Relative number of moles Simple ratio of moles Simplest whole number ratio of moles

Carbon( $C$ ) $85.7$ $12$ $\frac{85.7}{12} = 7.14$ $\frac{7.14}{7.14} = 1$ $1$

Hydrogen( $H$ ) $14.3$ $1$ $\frac{14.3}{1} = 14.3$ $\frac{14.3}{7.14} = 2.002$ $2$

Therefore, the empirical formula of the hydrocarbon P is ${CH}_{2}$ .

The empirical formula is a chemical formula representing the simplest ratio of atoms that are involved in the chemical formula whereas the molecular formula gives the actual number of each different atom present in a molecule. The molecular formula is a multiple of the empirical formula.

Molecular Formula $= n \times$ Empirical Formula, where $n$ is a positive whole number.

The empirical formula $({CH}_{2})$ mass is $= 12 + 2 \times 1 = 14$

The relative molecular mass of P is given $= 28$

We know, $n = \frac{Molar mass}{Empirical formula mass}$

So, $n = \frac{28}{14} = 2$

So, the molecular formula is $= n \times$ empirical formula $= 2 \times {CH}_{2} = C_{2} H_{4}$

The hydrocarbon has the formula $C_{2} H_{4}$ . Its IUPAC name is ethene.

The structural formula of the hydrocarbon P $(C_{2} H_{4})$ is as follows:

It contains one carbon-carbon double bond, with each of these carbon atoms also bonded to two hydrogen atoms. Its geometry is trigonal planar with ${sp}^{2}$ hybridisation.

A hydrocarbon P contains $14.3 %$ hydrogen.

(i) Find out its empirical formula.

(ii) The relative molecular mass of it is $28$ . Calculate its molecular formula.

(iii) Name the organic compound P.

(iv) Write the structural formula of P.

Important Questions on Practice Paper-10

Learn and Prepare for any exam you want !

A hydrocarbon P contains 14.3% hydrogen. (i) Find out its empirical formula. (ii) The relative molecular mass of it is 28. Calculate its molecular formula. (iii) Name the organic compound P. (iv) Write the structural formula of P.

Important Questions on Practice Paper-10

Learn and Prepare for any exam you want !

A hydrocarbon P contains $14.3 %$ hydrogen.

(i) Find out its empirical formula.

(ii) The relative molecular mass of it is $28$ . Calculate its molecular formula.

(iii) Name the organic compound P.

(iv) Write the structural formula of P.