hi guyz it is exam season! i dont feel like typing a real post so im just gonna do some sample problems hehehe 1. Sehee used a coffee cup calorimeter to dissolve 11.86 g of NH4NO3 in 100 mL of water. The initial temperature of the water was 20.5 degC. At the end of the reaction, the temperature recorded was 11.6 degC. Calculate the enthalpy change in kJ/mol of NH4NO3. Indicate if the reaction is exothermic or endothermic. (Heat capacity of water = 4.18 J/g degC) (5 marks) Answer: NH 4 NO 3 Water ΔH sol'n = ? kJ/mol m = 11.86 g M = 2M N + 4M H + 3M O M = [2(14) + 4(1) + 3(16)] g/mol M = 80 g/mol n = m/M n = (11.86 g) / (80 g/mol) n = 0.1483 mol m = 100 g T 1 = 20.5 degC T 2 = 11.6 degC ΔT = (20.5 - 11.6) degC ΔT = 8.9 degC nΔH sol'n = mcΔT n ΔH sol'n = mcΔT / n nΔH sol'n = (100 g)(4.18 J/g degC)(8.9 degC) / 0.1483 nΔH sol'n = 25086 J/mol (extra digits carried) nΔH sol'n = 25.1 kJ/mol the t
