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JAMB Chemistry 1986 Question 19

Question 19

Energy Changes

20 cm3 of 0.1 molar NH4OH solution when neutralized with 20.05cm3 of 0.1 molar HCl liberated 102 joules of heat. Calculate the heat of neutralization of NH4OH

  1. A.−51.0 KJ mol−1
  2. B.+57.3 KJ mol−1
  3. C.+57.0 kJ mol−1
  4. D.+51.0 kJ mol−1.
Show the answer and explanation

Answer: A (−51.0 KJ mol−1)

Explanation

Moles of NH4OH = 0.020 × 0.1 = 0.002 mol. 102 J / 0.002 = 51000 J = 51.0 kJ per mole, and since heat was given out, ΔH = −51.0 kJ mol−1.