How many grams of O2 will be obtained by decomposing 98.1 grams of kcl03

Iknow #2 is d. i just need to know why

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?

Adilute aqueous potassium nitrate solution is