Question

Ethene undergoes incomplete combustion to form carbon dioxide, carbon monoxide and water vapour. If the ratio of carbon dioxide to carbon monoxide formed is 9:1 when x cm^3 of ethene is burnt, what is the volume of oxygen gas consumed in the reaction?

Answer 1

Ethene undergoes incomplete combustion to form carbon dioxide, carbon monoxide and water vapour. The balanced equation of this incomplete combustion reaction is as follows.

`C_2H_4(g)+5/2O_2(g)->CO_2(g)+CO(g)+2H_2O(g)`

But as per question the ratio of volumes of `CO_2(g):CO(g)` produced is `9:1`. So this also represents the mole ratio of
`CO_2(g):CO(g)` produced.

Hence adjusting this ratio balanced equation may be written as follows
`10C_2H_4(g)+39/2O_2(g)->9CO_2(g)+CO(g)+20H_2O(g)`

Here we see `10cm^3` `C_2H_4(g)` will require `39/2=19.5cm^3"" ""O_2(g)`

So to burn `xcm^3` ethene the required volume of oxygen will be `19.5/10xx xcm^3=1.95xcm^3`