2CO(g) + O2(g) -> 2 CO2(g). What volume of oxygen is required at 25 degrees celcius?
This is all the information the question come with, and I am not sure if there might be something missing?
Note the correct spelling of Celsius.
Probably something is missing. With no volume CO listed you can't give a volume of O2 required.
However, with no volume CO listed, you could answer that the required amount of O2 required is 1/2 the volume of CO used.