text: I searched through my thermodynamics book for this, so I hope you appreciate it.\nFirst, you need a ballanced chemical equation.\n\n2N2H2 + O2 ---> 2H2O + 2N2\n\nC = 887.0 J/K = 0.8870 kJ/ K\nn = 1 mol (since it's a 2 to 2 relation, we can just say 1)\ndelta T = T = 4.20 ºC = 4.20 K\nq = ?\n\nq = CT/n = (0.8870 kJ/K * 4.20 K) / (1 mol) \n  =  3.73 kJ/mol\n\n\nHope this helps!