Calculating Enthalpy Change of Solution | A-Level Chemistry | AQA, OCR, Edexcel

Calculating Enthalpy of Solution We can use a Born-Haber cycle to calculate the enthalpy of solution using an indirect route. This involves breaking an ionic lattice to give gaseous ions (enthalpy of lattice dissociation) and then dissolving these gaseous ions in water (enthalpy of hydration). The equation used to calculate enthalpy of solution from a Born-Haber cycle is: Enthalpy of solution ΔHsol = lattice dissociation enthalpy + sum of hydration Using the principle of Hess's Law, we are able to work out the value of the enthalpy of solution for sodium chloride in this example. ΔHz = ΔHx + ΔHy = (+787) + (-346 + - (406) )= +17 kJ mol-1 Worked example: Calculate the enthalpy of solution of magnesium chloride given the following information. Lattice Enthalpy of MgCl2 (s) 2526 kJ mol-1 Enthalpy of hydration of Mg2+(g)-1891 kJ mol-1 Enthalpy of hydration of Cl-(g)-381 kJ mol-1 Answer: ΔHsol = ΔHlatt + [ΔHhydr (Mg2+) + 2 x ΔHhydr (Cl-) ] = 2526 + (-1891+(2 x -381)) = -127 kJ mol-1 As the enthalpy change is exothermic, it shows that magnesium chloride is soluble. 🔓 Unlock Full Course: https://courses.medicmind.co.uk/p/ale... 🔖 Past Papers: https://www.studymind.co.uk/resources/ 👩🏻‍🏫 1-1 Tutoring: https://www.studymind.co.uk/subject/a... #ALevelChemistry #Chemistry #A-LevelChemistry #StudyMind