For the reaction ?C6H6 + ?O2 → ?CO2 + ?H2O 27.3 grams of C6H6 are allowed to react with 73.81 grams of O2. How much CO2 will be produced by this reaction? Answer in units of grams.

Answer 1

First, we must write the correctly balanced equation:

2C₆H₆ + 15O₂ ==> 12CO₂ + 6H₂O ... balanced equation

Next, we need to find which reactant is limiting. We can do this by calculating mass of CO₂ produced from each reactant separately. The one that produces the least amount is limiting, and the amount produced from that reactant will be our answer.

27.3 g C₆H₆ x 1 mol C₆H₆/78.11 g x 12 mol CO₂ / 2 mol C₆H₆ x 44 g CO₂ / mol CO₂ = 92.3 g CO₂ formed

73.81 g O₂ x 1 mol O₂/32 g x 12 mol CO₂/15 mol O₂ x 44 g CO₂/mol CO₂ = 81.2 g CO₂ formed

So, the answer would be 81.2 g, but NOTE: this is a poor question because in reality, if O₂ is limiting (as in this problem), the combustion of C₆H₆ will be incomplete, and the balanced equation will NOT be what it is as written above. In more advanced chemistry courses, you will learn that CO and CO₂ are formed.