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.
Attributions and References
This page is adapted by Jackie MacDonald from:
- Salts (15.1) is adapted from “2.4 Inorganic Compounds Essential to Human Functioning” In Anatomy and Physiology 2e (Open Stax) by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix is licensed under CC BY 4.0. Access for free at Anatomy and Physiology 2e (OpenStax).
- Electrolytes (15.2) is adapted from “Ch. 11 Summary” In Chemistry 2e (Open Stax) by Paul Flowers, Klaus Theopold, Richard Langley & William R. Robinson is licensed under CC BY 4.0. Access for free at Chemistry 2e (OpenStax).
- Precipitation Reactions (15.3) is adapted from “6.2 Precipitation Reactions” In CHEM 1114 – Introduction to Chemistry (BCcampus, Pressbooks) by Shirley Wacowich-Sgarbi and Langara Chemistry Department is licensed under CC BY-NC-SA 4.0.
- Describing Reactions in Solutions by Writing Molecular, Complete Ionic, and Net Ionic Equations (15.4) is adapted from “4. 1 Writing and Balancing Chemical Equations” In CHEM 1114 – Introduction to Chemistry by Shirley Wacowich-Sgarbi and Langara Chemistry Department is licensed under CC BY-NC-SA 4.0.
Adaptations to aid in student comprehension by Jackie MacDonald.