Carbon-14 has a half-life of 5,730 years. in how many years will 120 grams of carbon-14 decay to 15 grams?

11,460 years
17,190 years
22, 920 years
28,650 years

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?