Question

Given the balanced equation representing a reaction occurring at 101.3 kilopascals and 298 k. 2h2(g) + o2(g) → 2h2o(l) + energy what is the net amount of energy released when one mole of h2o(l) is produced?

Answer 1

I believe the answer will be 285.8 kJ
The reaction above is for two moles of water; therefore we divide the amount of energy by half. 
The enthalpy of formation of a substance is the energy absorbed or released when one mole of a substance is formed from its constituents elements. For example the enthalpy of formation of water is 285.8 kJ/mol