Two trials are run, using excess water. In the first trial, 7.8 g of Na₂O₂(s) (molar mass 78 g/mol) is mixed with 3.2 g of S(s). In the second trial, 7.8 g of Na₂O₂(s) is mixed with 6.4 g of S(s). The Na₂O₂(s) and S(s) react as completely as possible. Both trials yield the same amount of SO₂(aq). Which of the following identifies the limiting reactant and the heat released, q, for the two trials at 298 K?
A. S 30. kJ
B. S 61 kJ
C. Na₂O₂ 30. kJ
D. Na₂O₂ 61 kJ