Question

Many homes in rural america are heated by propane gas, a compound that contains only carbon and hydrogen. Complete combustion of a sample of propane produced 2.641 g of carbon dioxide and 1.442 g of water as the only products. Find the empirical formula of propane.

Answer 1

Answer:

            C₃H₈

Solution:

Step 1: Calculating Moles for each Element:

C  =  Mass of CO₂ × (1 mol of CO₂÷ M.Mass of CO₂) × (1 mol of C ÷ 1 mol of CO₂)

C  =  2.641 g × (1 mol of CO₂÷ 44.011 g.mol⁻¹) × (1 mol of C ÷ 1 mol of CO₂)

C =  0.0600 mol

H  =  Mass of H₂O × (1 mol of H₂O ÷ M.Mass of H₂O) × (2 mol of H ÷ 1 mol of H₂O)

H  =  1.442 g × (1 mol of H₂O ÷ 18.106 g.mol⁻¹) × (2 mol of H ÷ 1 mol of H₂O)

H =  0.159 mol

Step 2: Calculate the Smallest whole number ratio as,

                                  C                                                        H

                               0.0600                                               0.159

                       0.0600/0.0600                                  0.159/0.0600

                                    1                                                    2.654

Multiply ratio by 3,

                                    3                                                      7.96

Or,

                                    3                                                        ≈ 8

Result:

           Empirical Formula of Propane is C₃H₈