Chapter 15 – Summary

15.1 Salts

Salts are a chemical compound formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged; overall the ionic compound has no net charge. Salts typically are crystalline, odourless, colourless/transparent or white, and have high melting and boiling points. Many salts are soluble in water; however, some are not. If a given salt is soluble in water, it completely dissociates into ions other than a hydrogen ion (H+) or hydroxide ion (OH) and forms an aqueous solution. This fact is elemental in distinguishing salts from acids and bases. Salts are derived from the neutralization reaction of an acid and base. Since acids and bases always contain either a metal cation or a cation derived from ammonium (NH4+) and a nonmetal anion, respectively, the two can combine to form a salt.

15.2 Electrolytes

Substances that dissolve in water to yield ions are called electrolytes. Electrolytes may be covalent compounds that chemically react with water to produce ions (for example, acids and bases), or they may be ionic compounds that dissociate to yield their constituent cations and anions, when dissolved. Dissolution of an ionic compound is facilitated by ion-dipole attractions between the ions of the compound and the polar water molecules. Soluble ionic substances and strong acids ionize completely and are strong electrolytes, while weak acids and bases ionize to only a small extent and are weak electrolytes. Nonelectrolytes are substances that do not produce ions when dissolved in water.

15.3 Precipitation Reactions

Chemical reactions are classified according to similar patterns of behaviour.  Precipitation is one type of chemical reaction which involves the formation of one or more insoluble products. Precipitation reactions, also called double displacement reactions can be summarized with the following reaction equation:

AB(aq) + CD (aq) → AD(s) + CB(aq) or (s)

The formation of the solid from combining two aqueous solutions is the driving force of the reaction (the factor that makes the reaction go). A precipitation reaction can be predicted to occur with the help of a solubility table.

15.4 Describing Reactions in Solutions by Writing Molecular, Complete Ionic, and Net Ionic Equations

Chemical equations are symbolic representations of chemical and physical changes. Chemical reactions in aqueous solution that involve ionic reactants or products may be represented more realistically by complete ionic equations and, more succinctly, by net ionic equations. Complete ionic and net ionic equations can be used to illustrate what is happening during precipitation reactions, neutralization reactions, gas evolving reactions, and single replacement reactions when these reactions occur in aqueous solutions.

Attribution & References

This page is adapted by Jackie MacDonald from:

Adaptations to aid in student comprehension by Jackie MacDonald.


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Enhanced Introductory College Chemistry Copyright © 2023 by Gregory Anderson; Caryn Fahey; Jackie MacDonald; Adrienne Richards; Samantha Sullivan Sauer; J.R. van Haarlem; and David Wegman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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