Question

Ethane burns in oxygen to form CO₂ and H₂O according to the equation:

\[\ce{2C2H6 + 7O2 -> 4CO2 + 6H2O}\]

If 1250 cc of oxygen is burnt with 300 cc of ethane, calculate:

1. the volume of CO₂ formed.
2. the volume of unused O₂.

Answer 1

By Lussac’s law:

\[\ce{\underset{2 vol{.}}{2C2H6} + \underset{7 vol{.}}{7O2} -> \underset{4 vol{.}}{4CO2} + 6H2O}\]

a. Since 2 volumes of C₂H₆ produce 4 volumes of CO₂:

Volume of CO₂ = `4/2 xx 300`

= 600 cc

b. Since 2 volumes of C₂H₆ require 7 volumes of O₂:

Volume of O₂ required = `7/2 xx 300`

= 1050 cc

Unused oxygen = 1250 − 1050

= 200 cc

Hence, the volume of unused oxygen is 200 cc.