Acid and Base in Medical Chemistry

Acids, Bases, and Salts

• Acids and bases are present naturally in nature, such as citric acid in fruits and hydrochloric acid in gastric juices.
• Many acids are used in daily life, such as vinegar and boric acid.

Definitions

• Acids (Arrhenius definition) are substances that form hydrogen ions (H+) when dissolved in water.
• Examples of acids include hydrochloric acid (HCl), which forms H+ when dissolved in water.

Types of Acids

• Natural Acids: obtained from natural sources, such as fruits and animal products (e.g., lactic and citric acids).
• Mineral Acids: prepared from minerals (e.g., hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3)).

Base and Alkali

• A base is a substance that forms hydroxide ions (OH-) when dissolved in water.
• Examples of bases include sodium hydroxide (NaOH), which forms OH- when dissolved in water.
• Bases are found in oral care products, such as toothpaste and mouthwashes, and help neutralize acids in the mouth.

The Bronsted-Lowry Theory

• Defines an acid as a proton donor and a base as a proton acceptor.

Measuring pH and its Scale

• pH is defined as the negative logarithm of H+ ion concentration.
• pH can be measured using a pH meter.
• The pH scale ranges from 0 to 14.
• pH of an acid is below 7 (acidic), pH of a base is above 7 (alkaline), and pH of 7 is neutral.
• pH of strong acid or base does not depend on temperature.
• pH of weak acid decreases with increase in temperature, while pH of weak base increases with increase in temperature.

Properties of Acids

• pH values are always less than 7.
• Aqueous solutions of acids are electrolytes.
• Acids have a sour taste.
• Blue litmus turns red in the presence of an acid.
• Acids are corrosives, reacting with active metals and causing slow-healing burns and tissue damage when concentrated.
• Acids react with active metals to yield hydrogen gas and with carbonates and bicarbonates to yield carbon dioxide gas.

Properties of Bases

• pH values are always greater than 7.
• Bases often have a bitter taste and are found in foods less frequently than acids.
• Aqueous solutions of bases are electrolytes.
• Red litmus turns blue in the presence of a base.
• Bases are alkalis, causing slow-healing burns and tissue damage when concentrated.

Salts

• Salt is produced by the reaction of an acid with a base.
• A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid.

Acids and Bases in Oral Health

• Maintaining a healthy balance between acids and bases in the mouth is essential for oral health.
• Saliva is slightly acidic (pH 6.2 to 7.4) and contains bicarbonate ions, which act as a buffering system to maintain pH balance in the mouth.
• Saliva helps neutralize acids produced by bacteria.