Acids, Bases, and Salts: Chemical Reactions Guide

Study Notes

Acids, Bases, and Salts: A Guide to Chemical Reactions and Properties

Acids, bases, and salts are fundamental concepts in chemistry, as they underpin the mechanisms of numerous chemical reactions and processes in our natural world. In this article, we'll delve into the properties, behavior, and reactions of these substances, starting with the basics.

Acids

An acid is a substance that donates protons (H⁺ ions) to other substances, when dissolved in water. This process is known as acid dissociation or ionization, where acids release hydrogen ions, making the solution acidic. Acids typically have a sour taste and can cause metals to corrode. Common household examples of acids include hydrochloric acid (HCl) and citric acid.

Acids have a characteristic acidic nature due to the presence of hydrogen-containing functional groups. For instance, carboxylic acids (such as acetic acid) have a hydroxyl group (OH) bonded to a carbonyl group (C=O). Sulfonic acids have sulfonyl groups (SO₃H), and phosphoric acid has phosphate groups (PO₃H₂).

Bases

A base is a substance that accepts protons (H⁺ ions) from other substances, when dissolved in water. This process is known as protonation, where bases gain hydrogen ions, making the solution basic. Bases often have a bitter or soapy taste and are slippery to the touch. Common household examples of bases include sodium hydroxide (NaOH) and ammonia (NH₃).

Like acids, bases have characteristic properties due to the presence of specific functional groups. For example, amines have nitrogen atoms (N) bonded to alkyl or aryl groups, while hydroxides have OH⁻ groups.

Acid-Base Reactions

Acid-base reactions, or proton transfer reactions, occur when acids and bases react with each other, resulting in the formation of a salt and water. Acid-base reactions are reversible, as the products can revert to their original substances. For instance, when hydrochloric acid reacts with sodium hydroxide, the products are sodium chloride and water.

[ \mathrm{HCl} + \mathrm{NaOH} \longrightarrow \mathrm{NaCl} + \mathrm{H}_2 \mathrm{O} ]

Types of Salts

A salt is formed when an acid and a base react. The salt consists of a cation from the base and an anion from the acid. Common salts include sodium chloride (NaCl) and potassium sulfate (K₂SO₄).

Salts have characteristic properties, such as solubility in water, conductivity, and reactivity. For example, ionic salts, like sodium chloride, are water-soluble and conduct electricity due to the free movement of their ions.

pH Scale

The pH scale is an indicator of acidity or alkalinity (basicity) in a solution. The pH scale ranges from 0 to 14, with values less than 7 being acidic, values greater than 7 being basic, and values of 7 being neutral. The pH scale is a logarithmic measure of the concentration of hydrogen ions in a solution, such that each decrease of one pH unit corresponds to a tenfold increase in the concentration of hydrogen ions.

To illustrate, a pH of 3 corresponds to 10 times more hydrogen ions than a pH of 4, while a pH of 11 corresponds to 10 times fewer hydrogen ions than a pH of 12.

Properties of Acids and Bases

Acids and bases exhibit several common properties, including:

Acids and bases have opposite effects on litmus paper and universal indicator, causing the paper to change color.
Acids and bases can react with metals, causing corrosion or hydrogen gas production.
Acids can neutralize bases, forming salts and water.
Acids and bases can react with each other in a reversible manner, forming salts, water, and an equilibrium.
Acids and bases can be strong or weak, depending on their ability to dissociate and release protons in aqueous solutions.

In summary, acids, bases, and salts are fundamental substances in chemistry, each characterized by their unique properties and reactions. The pH scale provides a useful tool for measuring and understanding the relative acidity and alkalinity of solutions, and acid-base reactions form the basis for a wide variety of chemical processes and reactions.

Description

Learn about the properties, behaviors, and reactions of acids, bases, and salts in chemistry. Explore the pH scale, acid-base reactions, substances' unique characteristics, and their effects on litmus paper and metals.