The heat of reaction for the following is −126 kJ. How much heat (kJ) would be evolved to the surroundings by the reaction of 25.0 g of Na2O2 with water?
2Na2O2 (s) + 2H2O (l) → 4NaOH (s) + O2 (g)
2Na2O2 = -126KJ
2 x 78g = -126KJ
1g = -126/(2 x 78)
25g = -126 x 25 / (2 x 78)