Question

Mg(s) + ½O2(g) → MgO(s) + 146 kcal/mole H2(g) + ½O2(g) → H2O(g), ΔH = -57.82 kcal/mole What type of reaction is represented by the previous two examples?

Answer 1

Answer is: both reactions are exothermic.

In exothermic reactions, heat is released and enthalpy of reaction is less than zero (as it show second chemical reaction).
According to Le Chatelier's principle when the reaction is exothermic heat is included as a product (as it show first chemical reaction).