The standard enthalpy of formation of CaSO 4 (s) at 25 ◦ C is − 1432 . 7 kJ mol − 1 .The equation that describes this formation reaction is: (A) CaSO 4 (s) −−→ Ca(s) S(s) 2 O 2 (g) (B) Ca(s) S(s) 2 O 2 (g) −−→ CaSO 4 (s) (C) Ca 2 (aq) SO 2 − 4 (aq) −−→ CaSO 4 (s) (D) CaSO 4 (s) −−→ Ca(s) S(s) 4 O(g) (E) Ca(s) S(s) 4 O(g) −−→ CaSO 4 (s)

Which of the following warnings would an agricultural chemist tell a farmer who wants to recycle his or her own ammonia? recycling ammonia is a difficult process that sometimes takes weeks. recycling ammonia requires a degree in biochemistry or a related field. recycling ammonia can be harmful because it is highly flammable and toxic. recycling ammonia costs too much money considering the price of the necessary chemicals.