Chapter 15: Reactions in Aqueous Solutions

We have learned in the previous section(s) that solutions are of extreme importance in everyday life. The food we eat, the liquids we drink, the fluids in our body, the air we breathe, and the household products we use, such as household cleaners, hand sanitizers, and medications, are all solutions. We often focus on solutions only being table salt dissolving in water when, actually, particles like pollutants suspended in the air are also solutions. This particular example is a gaseous solution. Metal alloys, such as brass (which is mix of copper and zinc), is an example of a solid solution.

This chapter will focus on reactions occurring specifically in aqueous solutions. Water is by far the most important liquid solvent, partly because it is plentiful and partly because of its unique properties. In your body, in other living systems, and in the outside environment a tremendous number of reactions take place in aqueous solutions. Consequently this section, as well as significant portions of many other sections of this text, are devoted to developing an understanding of reactions which occur in water. Since ionic compounds and polar covalent compounds constitute the main classes which are appreciably soluble in water, reactions in aqueous solutions usually involve these types of substances. There are three important classes of reactions which occur in aqueous solution: precipitation reactions, acid-base reactions, and oxidation-reduction (redox) reactions.

• Precipitation reactions are useful for detecting the presence of various ions and for determining the concentrations of solutions.
• Acid-base reactions and redox reactions are similar in that something is being transferred from one species to another.
  • Acid-base reactions involve proton transfers, whereas redox reactions involve electron transfers.
  • Redox reactions are somewhat more complicated, though, because proton transfers and other bond-making and bond-breaking processes occur at the same time as electron transfer.

Below are demonstrations of each of the types of reactions. Some of these reactions will be explained in detail in this chapter; others will be covered in more depth in later chapters.

The first video demonstrates precipitation reaction between aqueous solutions of silver nitrate and sodium chloride.

Watch Double Displacement Reaction of AgNO₃ and NaCl (41 sec)

The next video demonstrates an acid and base reacting with aluminum (in the form of a soda can) at room temperature. When alu­minum re­acts with hy­drochlo­ric acid, it yields aqueous alu­minum chlo­ride and col­our­less hy­dro­gen gas. When aluminum reacts with sodium hydroxide it forms water soluble sodium aluminate and hydrogen gas as products.
Watch Coke Cans in Acid and Base – Periodic Table of Videos (2min 49sec)

The last video shows a displacement reaction of zinc metal in aqueous copper (II) sulfate solution.
Watch Displacement Reaction of Metals – Zinc in Copper (II) Sulfate – with explanation at micro level (5min 45 sec).

Attribution & References

Except where otherwise noted, this section is adapted by Jackie MacDonald from “11.1: Prelude to Aqueous Phase Reactions” In ChemPRIME (LibreTexts CHEMISTRY) by Ed Vitz, John W. Moore, Justin Shorb, Xavier Prat-Resina, Tim Wendorff, & Adam Hahn, licensed under CC BY-NC-SA 4.0. / Adaptations and additions to content was updated for student comprehension.