When water is added to a mixture of Na2O2(s) and S(s), a redox reaction occurs, as represented by the equation below. 2NaO(s) + S(s) + 2H2O(l) —> 4NaOH(aq) + SO2(aq)
DH = 298 kJ/mol
DS = -7.3 J/(K•mol)

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