Ionic Equilibrium
Ionic Equilibrium - Related Videos
02:55
Solubility of Ionic Compounds
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2020
Solubility is the measure of the maximum amount of solute that can be dissolved in a given quantity of solvent at a given temperature and pressure. Solubility is usually measured in molarity (M) or moles per liter (mol/L). A compound is termed soluble if it dissolves in water. When soluble salts dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution; this process represents a physical change known as dissociation. Potassium chloride (KCl) is an example...
03:10
Ionic Radii
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2020
Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it is smaller than the atom from which it is derived. For example, the covalent radius of an aluminum atom (1s22s22p63s23p1) is 118 pm, whereas the ionic radius of an Al3+ (1s22s22p6) is 68 pm. As electrons are removed from the outer valence shell, the remaining core electrons occupying smaller shells experience a greater effective nuclear...
02:20
Dynamic Equilibrium
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2020
A reversible chemical reaction represents a chemical process that proceeds in both forward (left to right) and reverse (right to left) directions. When the rates of the forward and reverse reactions are equal, the concentrations of the reactant and product species remain constant over time and the system is at equilibrium. A special double arrow is used to emphasize the reversible nature of the reaction. The relative concentrations of reactants and products in equilibrium systems vary greatly;...
02:54
Molecular and Ionic Solids
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2020
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions. Molecular Solids Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
02:56
Free Energy and Equilibrium
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2020
The free energy change for a process may be viewed as a measure of its driving force. A negative value for ΔG represents a driving force for the process in the forward direction, while a positive value represents a driving force for the process in the reverse direction. When ΔGrxn is zero, the forward and reverse driving forces are equal, and the process occurs in both directions at the same rate (the system is at equilibrium). Recall that Q is the numerical value of the mass action expression...
FAQs
Equilibrium constants provide the quantitative link between forward and reverse ionic processes. For weak-acid ionization, the relevant constant relates the participating species and indicates how composition is distributed at equilibrium. For complex-ion formation, the corresponding constant describes association. Comparing these constants with concentration information helps chemists determine which ionic species are favored.
Changing concentration, solvent, or temperature can alter the position of an ionic equilibrium, so calculations must use the conditions of the solution being studied. These variables affect equilibrium relationships and therefore the amounts of ions available for subsequent reactions. Accounting for them is important when estimating pH, buffer capacity, solubility, or interacting-ion concentrations.
Mass balance accounts for the total quantity of a chemical component distributed among its ionic forms, whereas charge balance requires the solution's positive and negative charges to be consistent. Together with equilibrium expressions, these constraints connect unknown species concentrations. Applying all three prevents incomplete calculations and supports reliable results for pH, solubility, and interacting ions.
A practical analysis begins by identifying the interacting ionic species and writing the applicable equilibrium expressions. The calculation then incorporates the relevant mass-balance and charge-balance relationships under the specified concentration, solvent, and temperature conditions. Solving these relationships yields species concentrations or pH, while related results can describe buffer capacity or solubility.
In titration analysis, ionic-equilibrium calculations help relate solution composition to pH and the concentrations of reacting species. In precipitation and separation methods, the same principles describe how interacting ions are distributed and how solubility is assessed. These uses allow chemists to interpret analytical changes and select conditions for examining or separating dissolved components.
Water-quality assessment depends on understanding pH, solubility, and the concentrations of interacting ions, all of which can be evaluated with ionic-equilibrium principles. The same calculations contribute to designing chemical and biological systems by showing how ionic species are distributed under specified conditions. This provides a quantitative basis for assessing solution behavior and system composition.