Investigating the enthalpy of dissolution of ionic and polar substances in water

Abstract

Since water is a polar molecule with a bent structure, it dissolves many ionic and polar substances. Ionic solids are mostly soluble in water and water is the most common solvent of known ionic compounds. In an ionic solid, ions with opposite charges are held together through electrostatic attraction. The solubility of a substance in a solvent at a certain temperature is the maximum amount of that substance that dissolves in a certain volume of that solvent. As a result of the dissolution of one substance in another substance, three steps occur: separation of dissolved particles, separation of solvent particles, and mixing of solute particles and solvent particles. The first and second stages are endothermic due to the separation of the molecules of the solute substance and the solvent from each other, and the third stage is exothermic due to the merging of the molecules of the solute substance and the solvent. The enthalpy of dissolution of one mole of solute in a large amount of solvent is called the enthalpy of dissolution of the same substance. The dissolution process is associated with energy exchange, which is obtained by using the enthalpies of the solute substance, solvent, and hydration enthalpy in the form of enthalpy of solution. The enthalpy of the solution is also determined using the Brunhaber cycle. If the set of mentioned steps gives numbers with a positive sign, the process is endothermic and if the numbers with a negative sign are obtained, the process is exothermic. Scientists use this property of dissolution of materials to produce heat-generating and cold-generating packages, which are used for different purposes. The methods used in collecting information to achieve the desired goal are of the library type and quantitative and qualitative methods are also used.