C15H30 is a hydrocarbon that reacts with oxygen gas to give carbon dioxide and water.

Question

Calculate the mass of water (grams) formed when 724.05 grams of the hydrocarbon reacts with the oxygen gas.

Answer 1

This is a stoichiometry problem. Here is a worked example. Just follow the steps. You need not convert grams to moles since you are given moles initially.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Answer 2

C15H30 +02 -> CO2 + H2O

Im having trouble balancing it.
Thank you

Answer 3

2C15H30 + 45O2 ==> 30CO2 + 30H2O