Solubility and Complex-Ion Equilibria

Comprehensive practice vocabulary flashcards covering Solubility Product Constants, the Common-Ion Effect, Precipitation, pH effects, Complex-Ion Formation, and Qualitative Analysis of Metal Ions.

Solubility Product Constant ($K_{sp}$)

The equilibrium constant for the solubility equilibrium of a slightly soluble (or nearly insoluble) ionic compound, equal to the product of the equilibrium concentrations of the ions, each raised to a power equal to its stoichiometric coefficient.

Solubility Equilibrium

An equilibrium that occurs between the solid compound and the ions in a saturated solution when an excess of a slightly soluble ionic compound is mixed with water.

Molar Solubility ($x$)

The number of moles of solute dissolved in a given volume of a saturated solution, typically expressed in units of $mol/L$.

Mass per Volume Solubility

The number of grams of solute dissolved in a given volume of a saturated solution.

Common-Ion Effect

The phenomenon where the solubility of an ionic compound decreases due to the addition of a soluble compound that contains an ion already present in the equilibrium system.

Ion Product ($Q_c$)

The product of ion concentrations in a reaction mixture, each raised to the power of its stoichiometric coefficient at a particular point in time, used to determine if precipitation will occur.

Supersaturated Solution

A condition where the ion product ($Q_c$) for a solubility reaction is greater than the solubility product ($K_{sp}$), leading to the expectation of precipitation.

Unsaturated Solution

A condition where the ion product ($Q_c$) is less than the solubility product ($K_{sp}$), meaning precipitation will not occur.

Fractional Precipitation

The technique of separating two or more ions from a solution by adding a reactant that precipitates one ion at a time based on differences in their solubilities.

Qualitative Effect of pH on Solubility

The principle stating that salts of weak acids are more soluble in acidic solutions because the removal of the anion by reaction with $H_3O^+$ drives more solid to dissolve.

Complex Ion

An ion formed when a metal ion reacts with molecules or ions (ligands) that have lone pairs of electrons to form coordinate covalent bonds.

Formation Constant ($K_f$)

The equilibrium constant for the formation of a complex ion from an aqueous metal ion and its ligands; also known as the stability constant.

Dissociation Constant ($K_d$)

The equilibrium constant for the dissociation of a complex ion, which is the reciprocal or inverse value of the formation constant ($K_d = \frac{1}{K_f}$).

Amphoteric Hydroxide

A metal hydroxide, such as $Al(OH)_3$ or $Zn(OH)_2$, that behaves as both a base (reacting with acids) and an acid (reacting with bases).

Qualitative Analysis of Metal Ions

A systematic chemical procedure used to separate and identify cations in a mixture through characteristic precipitation reactions.

Analytical Group 1

Metal ions ($Ag^+$, $Hg_2^{2+}$, and $Pb^{2+}$) that are separated from a mixture by precipitation as chlorides using dilute $HCl(aq)$.

Analytical Group 2

Metal ions such as $Cu^{2+}$, $Cd^{2+}$, and $Sn^{4+}$ that are precipitated as sulfides from a solution that is $0.300016 M H_3O^+$ and saturated with $H_2S$.

Analytical Group 3

Metal ions like $Co^{2+}$, $Fe^{2+}$, and $Zn^{2+}$ that are precipitated as sulfides (or hydroxides like $Al(OH)_3$) in a weakly basic solution with $H_2S$.

Analytical Group 4

Alkaline earth ions ($Ba^{2+}$, $Mg^{2+}$, $Ca^{2+}$, and $Sr^{2+}$) precipitated from the filtrate as carbonates or phosphates by adding $(NH_4)_2CO_3$ or $(NH_4)_2HPO_4$.

Analytical Group 5

Alkali metal ions ($K^+$ and $Na^+$) that remain in the solution (filtrate) after the precipitations of Groups 1 through 4 are complete.

Filtrate

The solution that remains after the precipitate has been removed by passing through a filter.

Stoichiometry of $K_{sp}$ for $AB_3$

The mathematical relationship expressed as $K_{sp} = [x][3x]^3 = 27x^4$, where $x$ represents the molar solubility.