From the following reactions, determine the heat of reaction: Cu2S (s) + 2 O2 (g)  2 CuO (s) + SO2 (g) (1) SO2 (g)  S (s) + O2 (g) H = 298 kJ (2) Cu(s) +  O2(g)  CuO(s) H = -146 kJ (3) Cu (s) +  S (s)   Cu2S (s) H = -40 kJ