Many people use propane gas grills to cook the perfect

Question

1. There is nothing like the smell of BBQ in the summertime. Many people use propane gas grills to cook the perfect steak. Here is the unbalanced reaction that is occurring while the steak sizzles on the grill:

C₃­H₈(g)  + O₂(g) --> CO₂(g) +  H₂O (g)

The balanced reaction has a ΔH^o_rxn = -2217 kJ. If a steak must absorb 7.2x10^-4 kJ to reach a perfect medium rare, and if only 15% of the heat produced by the barbeque is actually absorbed by the steak, what mass of H₂O is emitted into the atmosphere when this steak is cooked? (Hint: don't forget to balance the reaction).