The equation for the combustion of methane is CH4+ 2O2——->CO2+2H2O

if you have 5 moles of oxygen how many moles of CO2 could be produced?

the moles of CO2(g) =2.5moles

I hope this help

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.