The volume of oxygen gas and carbon monoxide that need to react is calculated as follows
write the equation for reaction
2CO +O2= 2CO2
the reacting ratio of CO:O2:CO2 is 2:1:2 from the equation above therefore
the volume of O2 = 4.86l x 1/2=2.43 L of O2
the volume of CO = 4.86 x2/2 = 4.86 L of CO