Acidic

Acidic

Acidity is a fundamental concept in chemistry and biology, referring to the property of a substance that increases the concentration of hydrogen ions (H⁺) in a solution. This property is quantitatively measured by the pH scale, where a pH less than 7 indicates an acidic solution. Acids play crucial roles in various biological processes and industrial applications.

Definition

An acidic substance is one that donates protons (H⁺ ions) to other substances. According to the Brønsted–Lowry acid–base theory, an acid is a proton donor, while a base is a proton acceptor. The strength of an acid is determined by its ability to donate protons, which is often represented by its dissociation constant (Ka).

pH Scale

The pH scale is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is defined as the negative logarithm of the hydrogen ion concentration:

\[ pH = -\log[H⁺] \]

A pH of 7 is considered neutral, while a pH less than 7 indicates an acidic solution. The lower the pH, the more acidic the solution.

Common Acids

Some common acids include:

• Hydrochloric acid (HCl) - Found in gastric acid in the stomach.
• Sulfuric acid (H₂SO₄) - Used in car batteries and industrial processes.
• Acetic acid (CH₃COOH) - The main component of vinegar.
• Citric acid (C₆H₈O₇) - Found in citrus fruits.

Biological Importance

Acids are vital in biological systems. For example, the stomach secretes hydrochloric acid to aid in digestion and to kill harmful bacteria. Cellular respiration produces carbonic acid as a byproduct, which is then converted to bicarbonate for transport in the blood.

Industrial Applications

Acids are used in a wide range of industrial applications. Sulfuric acid is used in the production of fertilizers, while acetic acid is used in the manufacture of plastics and as a food preservative.

Safety and Handling

Acids can be corrosive and must be handled with care. Proper safety equipment, such as gloves and goggles, should be used when working with strong acids. In case of skin contact, the affected area should be rinsed with plenty of water.

Also see

• Base (chemistry)
• pH
• Neutralization (chemistry)
• Buffer solution