General Chemistry
The solubility product constant (Ksp) describes how easily an ionic substance dissolves in a given solvent. It is calculated while a solution is in dynamic equilibrium, where the forward and backward reaction rates are equal. Ksp is similar to the equilibrium constant (Keq); however, reactants are not included in the Ksp calculation because pure solids and liquids don't change ion concentrations. A higher temperature typically increases Ksp for solids but decreases the solubility of gases in a liquid, while higher pressure increases the solubility of a gas in a liquid.
The solubility product quotient (Qsp) has the same equation as Ksp but uses concentrations at a given point in time (typically when the solvation is not equilibrium). Comparing Qsp and Ksp helps determine if a solution is unsaturated (Qsp < Ksp), supersaturated (Qsp > Ksp), or saturated and in equilibrium (Qsp = Ksp). Molar solubility is the molarity of a saturated solution. The common ion effect states that the solubility of a compound in a solution is reduced if the solution already contains one of the ions in the compound. This occurs because the solvent cannot dissolve as much of the new solute due to the presence of the common ion.
Lesson Outline
<ul> <li>Solubility Product Constant (Ksp) <ul> <li>Describes how easily an ionic substance dissolves in a given solvent</li> <li>Calculated while a solution is in dynamic equilibrium</li> <li>Similar to the equilibrium constant (Keq) but doesn't include reactants</li> <li>Temperature and pressure effects on Ksp: <ul> <li>Higher temperature increases Ksp for solids, decreases for gases</li> <li>Higher pressure increases Ksp for a gas being dissolved into a liquid</li> </ul> </li> </ul> </li> <li>Solubility Product Quotient (Qsp) <ul> <li>Has the same equation as Ksp but uses concentrations of ions not in equilibrium</li> <li>Comparing Qsp and Ksp helps determine solution saturation: <ul> <li>Unsaturated: Qsp < Ksp</li> <li>Supersaturated: Qsp > Ksp</li> <li>Saturated and in equilibrium: Qsp = Ksp</li> </ul> </li> <li>Molar solubility is the molarity of a saturated solution</li> </ul> </li> <li>Common Ion Effect <ul> <li>States that solubility of a compound is reduced if the solution contains one of the compound's ions</li> <li>Occurs because the solvent cannot dissolve as much of the new solute due to the presence of the common ion</li> </ul> </li> </ul>
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FAQs
The solubility product constant (Ksp) is a specific type of equilibrium constant (Keq) that applies to the dissolution of sparingly soluble ionic compounds in water. Ksp is used to describe the equilibrium between a solid ionic compound and its dissociated ions in a solution. It is similar to Keq in that both describe the relative concentrations of reactants and products at equilibrium, but Ksp specifically focuses on the solubility of ionic compounds.
The common ion effect occurs when an ionic compound is dissolved in a solution that already contains one of its constituent ions. The presence of the common ion reduces the solubility of the ionic compound, essentially shifting the equilibrium towards the solid compound rather than the dissociated ions. This is because the increased concentration of the common ion causes the solubility product quotient to exceed the Ksp value, favoring the formation of the solid compound and reducing overall solubility.
Molar solubility is a measure of the maximum number of moles of a solute that can dissolve in a liter of a solution before reaching saturation. On the other hand, the solubility product constant (Ksp) represents the equilibrium between a solid ionic compound and its dissociated ions in a solution. While molar solubility is related to Ksp, they are not the same thing. Molar solubility can be calculated from Ksp by considering the stoichiometry of the dissolution reaction and solving the associated chemical equation.
The solubility product quotient (Qsp) is calculated the same way as the solubility product constant (Ksp), but using the actual concentrations of the ions in a solution rather than the concentrations at equilibrium. Comparing the Qsp value to the Ksp value can help predict whether a precipitate will form or dissolve: if Qsp > Ksp, the solution is supersaturated, and precipitation is likely; if Qsp < Ksp, the solution is unsaturated, and the ionic compound is more likely to dissolve; if Qsp = Ksp, the solution is saturated, and the system is at equilibrium.
The solubility of an ionic compound and its solubility product constant (Ksp) can be influenced by several factors, including temperature, pressure, and the presence of other ions in the solution (such as the common ion effect). Temperature has a significant impact on solubility, as increasing temperature often increases the solubility of solids in water. However, the effect of temperature on Ksp can be different for different compounds. Pressure typically has a minimal effect on the solubility of solids but can be more significant for gases dissolved in water. Lastly, the common ion effect can reduce the solubility of an ionic compound due to the presence of a common ion in the solution, shifting the equilibrium towards the formation of the solid compound.
