Chemistry - Thermochemistry Question with Solution | TestHub
A volume of 100 ml of 0.5 N-HNO3 solution is neutralized with 300 ml of 0.25 M-NH4OH in a constant pressure calorimeter which resulted 1.7°C rise in temperature. The heat capacity of the calorimeter system is 1.5 kJ/°C. The enthalpy of neutralization of a strong acid with a strong base is -57 kJ/mol. Which of the following statements are correct? (one or more than one correct)
Options:(select one or more)
Answer:
Solution:
HNO3 = 0.1 × 0.5 = 0.05 mol; NH4OH = 0.3 × 0.25 = 0.075 mol, so HNO3 is limiting (0.05 mol of water formed). Heat evolved = 1.5 × 1.7 = 2.55 kJ (c false, 3.825 would use 0.075 mol). Per mole: 2.55/0.05 = 51 kJ, so ΔHneut = -51 kJ/mol (a true). Ionization of NH4OH absorbs 57 - 51 = 6 kJ/mol (b true). H2O → H+ + OH- is the reverse of strong acid-base neutralization, +57 kJ, not 51 (d false). Ans (a),(b).
