And then (ii) equiv quantities of reactant and product:
#"Moles of butane"# #=# #(5.80*g)/(58.12*g*mol^-1)=0.0998*mol#
#"Moles of dioxygen"=(1*atmxx15.0*L)/(0.0821*L*atm*K^-1*mol^-1xx273.15K)=0.669*mol#
(This is not quite #"STP"#, but you will have to adapt this expression.) At any rate there is stoichiometric dioxygen for complete combustion, which we must presume.
Given the equation (i), #4xx0.0998*mol# #CO_2# are evolved per equiv butane.
#V=(nRT)/P#
#=(4xx0.0998*molxx(0.0821*L*atm)/(K*mol)xx273.15K)/(1*atm)=8.95L#
And thus approx. #9*L# carbon dioxide gas evolve from complete combustion.