To solve this exercise you need to know that to create CO₂ with C₂H₂ is necessary to have oxygen. So, the following balanced equation represents the reaction:
2C₂H₂(g) + 5O₂(g) → 4CO₂(g) + 2H₂O(g)
Notice that 2 moles of C₂H₂ form 4 moles of CO₂, so if 3.3 moles of C₂H₂ react, how many moles of CO2 would be produced?
2 moles of C₂H₂ -------4 moles of CO₂
3.3 moles of C₂H₂--------x moles of CO₂
x=6.6 moles of CO₂ produced.
