# 11: Acids and Bases


• 11.1: Acids- Properties and Examples
Acids are very common in some of the foods that we eat. Citrus fruits such as oranges and lemons contain citric acid and ascorbic acid, which is better known as vitamin C. Carbonated sodas contain phosphoric acid. Vinegar contains acetic acid. Your own stomach utilizes hydrochloric acid to digest food. Acids are a distinct class of compounds because of the properties of their aqueous solutions.
• 11.2: Molecular Definitions of Acids and Bases
Although the properties of acids and bases had been recognized for a long time, it was Svante Arrhenius in the 1880's who determined that: the properties of acids were due to the presence of hydrogen ions, and the properties of bases were due to the presence of hydroxide ions.
• 11.3: Strong and Weak Acids and Bases
Acids are classified as either strong or weak, based on their ionization in water. A strong acid is an acid which is completely ionized in an aqueous solution. A weak acid is an acid that ionizes only slightly in an aqueous solution. Acetic acid (found in vinegar) is a very common weak acid.
• 11.4: Strong and Weak Acids and Acid Ionization Constant $$\left( K_\text{a} \right)$$
• 11.5: Water - Acid and Base in One
Water is an interesting compound in many respects. Here, we will consider its ability to behave as an acid or a base. In some circumstances, a water molecule will accept a proton and thus act as a Brønsted-Lowry base.
• 11.6: The pH and pOH Scales - Ways to Express Acidity and Basicity
pH and pOH are defined as the negative log of hydrogen ion concentration and hydroxide concentration, respectively. Knowledge of ether can be used to calculate either [H+] of [OH-]. pOH is related to pH and can be easily calculated from pH.
• 11.7: Reactions of Acids and Bases
When an acid and a base are combined, water and a salt are the products. Salts are ionic compounds containing a positive ion other than H+ and a negative ion other than the hydroxide ion, OH-. Double displacement reactions of this type are called neutralization reactions. Salt solutions do not always have a pH of 7, however. Through a process known as hydrolysis, the ions produced when an acid and base combine may react with the water to produce slightly acidic or basic solutions.
• 11.8: Acid–Base Titration
Acid-base titrations are lab procedures used to determine the concentration of a solution. One of the standard laboratory exercises in General Chemistry is an acid-base titration. During an acid-base titration, an acid with a known concentration (a standard solution) is slowly added to a base with an unknown concentration (or vice versa). A few drops of indicator solution are added to the base. The indicator will signal, by color change, when the base has been neutralized (when [H+] = [OH-]).
• 11.9: Buffers are Solutions that Resist pH Change
A buffer is a solution that resists dramatic changes in pH. Buffers do so by being composed of certain pairs of solutes: either a weak acid plus a salt derived from that weak acid or a weak base plus a salt of that weak base.

11: Acids and Bases is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.