On passing 2 litres of a mixture of CO and CO2 over red hot charcoal, the volume becomes 2.5 litres. The volume fraction of Co in the mixture is

Answer 1

So, some of the CO2 became CO.

CO2+ C> 2CO

If you assume all the CO2 was converted, then the the added volume of .5 liters equals the new CO, minus the original CO2

2.5litersCO= xlitersCOoriainal+ 2(2-x)liters CO new.

2.5=x+4-2x if my algebra is right, so
-1.5=-x
or the original amount of CO was 1.5, or 3/4 of the original mixture was CO.