One litre of CO2 is passed through red hot coke

Explanation:
The reaction upon passing CO2 over red hot  coke(C) is :
          CO2+C2CO
Based upon Gay-Lussac's law, 1 vol.of CO2 yields 2 vol of CO.
So, consider a L of CO2 giving 2a L of CO.
Volume of CO2 left=1-a  (Since, 1 litre of CO2 is passed)
Given, total volume =1.4 L
So,the remnant volume of CO2 and vol.of CO formed can be summed as follows(coke is solid, vol=0):
1-a+2a=1.4
1+a=1.4
Upon solving, a=0.4L
So, volume of CO=2a=2x0.4L=0.8 L
Similarly,Volume of CO2=1-a=1-0.4=0.6L
Final Answer:
Hence, the composition of the final product is 0.6L CO2 (remnant)and 0.8 L CO(formed) .