How much potassium nitrate has to dissolve in water to absorb 111 kJ of heat?
Wednesday, August 18th, 2010 at
8:08 PM
Potassium nitrate has a lattice energy of -163.8 kcal/mol and a heat of hydration of -155.5 kcal/mol.
Express answer in kg.
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How much potassium nitrate has to dissolve in water to absorb 111 kJ of heat?
Potassium nitrate has a lattice energy of -163.8 kcal/mol and a heat of hydration of -155.5 kcal/mol.
1 J = 4.19 cal
1 kJ = 4.19 Kcal
111 kJ = 464.7 kcal
lattice energy of -163.8 kcal/mol is required to break the bonds in the lattice
heat of hydration of -155.5 kcal/mol.is released as the KNO3 is hydrated and becomes more stable
Since lattice energy is required and energy of hydration is released, the net result is 8.3 Kcal of heat energy is required to dissolve a mole of KNO3 in 200 moles of water.
163.8 - 155.5 = 8.3Kcal / mole
8.3Kcal / mole * x moles = 464.7 kcal
Moles = 56 moles of KNO3
Molar mass of KNO3 = 39.1 + 14 +(3 * 16) = 101.1g/mole
101.1g/mole * 56 moles =5661.6 g of KNO3
5661.6 g of KNO3 = 5.6616 Kg of KNO3