Question

Calculate the heat of crystallization in kJ/mol of a substance, given that 100 g of it dissolved in water and cooled from 60°C to 20°C, releasing 5490 J of heat. The molar mass of the substance is 120 g/mol.

Answer 1

First, we need to determine the number of moles of the substance. We can do this by dividing the mass of the substance by its molar mass:moles = mass / molar massmoles = 100 g / 120 g/molmoles = 0.833 molNow, we know that the substance released 5490 J of heat when it dissolved in water and cooled from 60C to 20C. To find the heat of crystallization per mole, we need to divide the total heat released by the number of moles:heat of crystallization = heat released / molesheat of crystallization = 5490 J / 0.833 molheat of crystallization = 6590 J/molFinally, we need to convert the heat of crystallization from J/mol to kJ/mol:heat of crystallization = 6590 J/mol *  1 kJ / 1000 J heat of crystallization = 6.59 kJ/molSo, the heat of crystallization of the substance is 6.59 kJ/mol.