$$O_2\left(g\right)\ +\ 2\ H_2\ \left(g\right)\ \rightarrow\ 2\ H_2O\ \left(g\right)\ +\ Energy$$  

A student mixed two chemicals to allow them to react. The temperature before the reaction was 25 ° C. The temperature after the reaction was 18° C. Which of the following is true?

Are the products or reactants of this reaction storing more energy in their chemical bonds?

What kind of equation is this: 2KI + MgCl₂ + 200KJ ----> 2KCl + MgI₂

Which type of reaction does this graph represent?

When new chemical bonds form, energy ____________.

For the reaction 2H₂(g) + O₂(g) → 2H₂O(g) the bond enthalpies (in kJ/mol) are

H-H = x, O=O = y, O-H = z

Which calculation will give the value, in kJ/mol, of ΔH for the reaction?