Question

3. The molar heat of solution for ammonium nitrate (NH 4 NO 3 ) is 25.7 kJ/mol.

How many moles of NH 4 NO 3 (s) must be dissolved in water so that 88.0 kJ of
heat is released from the water (this process is endothermic -- the heat is
being absorbed as the ions break apart)

Answer 1

• 3.42 moles

Step-by-step explanation:

By the law of conservation of energy, assuming no losses of heat to the surroundings, the amount of heat consumed by the dissolution of the ammonium nitrate is equal to the amount of heat released from the water. This is, the ammonium nitrate absorbs all the heat it needs to break the ions apart and get dissolved from the water in which it is being dissolved.

Thus:

• 88.0kJ = n × 25.7 kJ/mol

↑ ↑ ↑

heat released number of moles molar heat of solution

from water of NH₄NO₃ for NH₄NO₃

Solve for n and compute:

• n = 88.0kJ / (25.7kJ/mol) = 3.42 moles ← answer