Question

The composition of air by volume is approximately 1/5 oxygen, 4/5 nitrogen.
When air is passed through red-hot carbon, the following reaction occurs:
2C + O2(g) 2CO(g). Ifall of the oxygen is converted to carbon
monoxide, what is the composition,by volume, of the gas produced?

Answer 1

If you look at the molar ratio, you can tell that for every \(O_2\) molecule, you get 2 CO molecules. So the volume, in fact, doubles.

So the 0.2 became 0.4, right?

If you want the Nitrogen into account, you have to know what you started with, 0.8 (which is 4/5).

now you have 0.4 CO and 0.8 \(N_2\)..

the percent composition of CO in the air is \(\dfrac{0.4}{0.4+0.8}\)