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Solubility will also depend on the excess or deficiency of a common ion in the solution [clarification needed], a phenomenon known as the common-ion effect. To a lesser extent, solubility will depend on the ionic strength of solutions. The last two effects can be quantified using the equation for solubility equilibrium.
The Hildebrand solubility parameter is the square root of the cohesive energy density: δ = Δ H v − R T V m . {\displaystyle \delta ={\sqrt {\frac {\Delta H_{v}-RT}{V_{m}}}}.} The cohesive energy density is the amount of energy needed to completely remove a unit volume of molecules from their neighbours to infinite separation (an ideal gas ).
A sodium ion solvated by water molecules. Solvations describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of the solvent such as its ...
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
The crystal structures of solute and solvent must be similar. Complete solubility occurs when the solvent and solute have the same valency. [2] A metal is more likely to dissolve a metal of higher valency, than vice versa. [1] [3] [4] The solute and solvent should have similar electronegativity.
Hansen solubility parameters were developed by Charles M. Hansen in his Ph.D thesis in 1967 [1] [2] as a way of predicting if one material will dissolve in another and form a solution. [3] They are based on the idea that like dissolves like where one molecule is defined as being 'like' another if it bonds to itself in a similar way.
^ The enthalpy is the internal energy corrected for any pressure-volume work at constant (external) . We are not making any distinction here. This allows the approximation of Helmholtz free energy, which is the natural form of free energy from the Flory–Huggins lattice theory, to Gibbs free energy.
The parameters may be derived from various experimental data such as the osmotic coefficient, mixed ion activity coefficients, and salt solubility. They can be used to calculate mixed ion activity coefficients and water activities in solutions of high ionic strength for which the Debye–Hückel theory is no longer adequate.