# What is the total volume of gaseous products formed when 199 liters of carbon monoxide react completely according to the following reaction? (All gases are at the same temperature and pressure.) "CO(g) + H"_2"O(g)"rarr"CO"_2("g") + "H"_2("g")"

Would this not be $398 \cdot L$?
You got $C O \left(g\right) + {H}_{2} O \left(g\right) \rightarrow C {O}_{2} \left(g\right) + {H}_{2} \left(g\right)$...
If ONE MOLE of carbon monoxide reacts you get ONE mole of carbon dioxide, and ONE mole of dihydrogen. If $25.4 \cdot L$ carbon monoxide reacts you get $25.4 \cdot L$ carbon dioxide, AND $25.4 \cdot L$ of dihydrogen. That is under standard conditions, the which we assume, volume is PROPORTIONAL to the number of gaseous particles, i.e. proportional to the number of MOLES....
And so if $199 \cdot L$ $C O$ react quantitatively, the stoichiometry INSISTS, that we get $199 \cdot L$ carbon dioxide, and $199 \cdot L$ dihydrogen, almost half a cubic metre of gas...