A mixture of CO and CO2 with a volume of 20 ml was combined with 20 ml of oxygen and set on fire, the volume

A mixture of CO and CO2 with a volume of 20 ml was combined with 20 ml of oxygen and set on fire, the volume of the mixture became 36 ml. Determine the composition of the initial mixture

Given:
V mixture (CO, CO2) = 20 ml
V (O2) = 20 ml
V mixture2 = 36 ml

To find:
φ (CO) -?
φ (CO2) -?

Decision:
1) 2CO + O2 => 2CO2;
CO + O2 – the reaction does not proceed;
2) Let V (CO) = (x) ml, then V (CO2) = (20 – x) ml;
3) V react. (O2) = V (CO) / 2 = (x / 2) ml;
4) V rest. (O2) = V (O2) – V react. (O2) = (20 – (x / 2)) ml;
5) V arr. (CO2) = V (CO) = (x) ml;
6) V mixture2 = V (CO2) + V rest. (O2) + V arr. (CO2);
36 = (20 – x) + (20 – (x / 2)) + x;
x = 8;
V (CO) = x = 8 ml;
7) φ (CO) = V (CO) * 100% / V mixture (CO, CO2) = 8 * 100% / 20 = 40%;
8) φ (CO2) = 100% – φ (CO) = 100% – 40% = 60%.

Answer: The volume fraction of CO is 40%; CO2 – 60%.