Thermochemical Equations Answers

Which substances have Hf = 0 kJ/mol by definition? Select all that apply.

Is this reaction endothermic or exothermic?

Water forms according to the equation below:2H2(g) + O2(g) 2H2O(g) Hrxn = -483.64 kJHow much energy is released during the formation of 1 mol H2O(g)? kJ

The synthesis reaction to form boron hydride is: 2B(s) + 3H(g) BH(g), H = +36 KJ. What is the enthalpy value for the manipulated reaction: 1/2BH(g) B(s) + 3/2H(g)?