Lattice energy of potassium nitrate (KNO3) = -163.8 kcal/mol
Hydration energy of KNO3 = -155.5 kcal/mole
Heat of solution is the amount of heat absorbed by water when 1 mole of KNO3 is dissolved in it
Heat of solution = Hydration energy - Lattice energy
= -155.5 -(-163.8) = 8.3 kcal/mol
1 kcal/mol = 4.184 kJ/mole
Therefore, 8.3 kcal/mole = 4.184 * 8.3 = 34.73 kJ/mol
Now, 34.73 kJ of heat is absorbed when 1 mole of KNO3 is dissolved
The given 105 kJ of heat would correspond to : 105/34.73 = 3.023 moles of KNO3
Molar mass of KNO3 = 101.1 g/mole
Mass of KNO3 = Molar mass * moles
= 101.1 * 3.023 = 305.63 g = 0.3056 kg
