need chemistry help

Question

if 2.08 moles of propane (C3Hg) react with excess oxygen in a complete combustion reaction, how many moles of water are produced?

Answer 1

Hello, Molly,

We need to have a balanced equation of the reaction to answer this question. It would be helpful to have one already worked out, unless that is part of the reason you asked the question.

C₃H_g, I suspect, was meant to be C₃H₈, Hg is mercury, a favorite element of mine, and it has more pride than to be caught with three carbons hanging on. :)

My try at a balanced reaction: 1C₃H₈ + 5O₂ = 3CO₂ + 4H₂O

This tells us we'll get 4 moles of water for every mole of propane. Use this molar ratio (4 moles H₂O/1 mole C₃H₈) to find the moles water theoretically produced.

(4 moles H₂O/1 mole C₃H₈)*(2.08 moles C₃H₈) = 8.32 moles H₂O

This is how many moles of water we should expect, assuming excess O₂ and good lab technique.

Bob