Iwill reward there are 3 answers

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Modern weaponry has increased the number of deaths in wars and violent conflicts.

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) 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?