10ml of CO is mixed with 25ml air having 20%  O2 by volume.  What would be the final volumes and the gases present, if none of CO and O2is left after the reaction?

2CO+O2→2CO2      oxygen is 20% of 25ml air  =25×20100=5ml  initial    :     10ml    5ml           0 reacted  :     10ml    5ml         10ml final       :       0           0          10ml