A hydrocarbon is burnt completely to give 3.447g of
C
O
2
and 1.647g of
H
2
O
. What is the empirical formula ?

The answer to your question is C₃H₇

Explanation:

Data

mass of CO₂ = 3.447 g

mass of H₂ = 1.647 g

Empirical formula = ?

Process

1.- Write the chemical reaction

                       CxHy + O₂   ⇒     CO₂   +   H₂O

2.- Calculate the mass and moles of carbon

                      44 g of CO₂ 12 g of C

                       3.447 g  of CO₂  x

                       x = (3.447 x 12) / 44

                       x = 0.94 g of C

                       12 g of C 1 mol

                       0.94 g of C  x

                       x = 0.0783 moles of C

3.- Calculate the grams and moles of H

                       18 g of H₂O  2 g of H

                       1.647 g of H₂O  x

                        x = (1.647 x 2)/18

                        x = 0.183 g of H

                       1 g of H     1 mol

                        0.183 g      x

                        x = (0.183 x 1)/1

                        x = 0.183 mol of H

4.- Divide by the lowest number of moles

Carbon = 0.0783 /0.0783 = 1

Hydrogen = 0.183 / 0.0783 =2.3

5.- Write the empirical formula

                          C₁H₂.₃ = 3C₁H₂.₃ = C₃H₇

the answer your looking for is c).