Acids are substances that taste sour, turn blue litmus paper red, and react with bases to form salts.
Arrhenius Theory: According to Svante Arrhenius, acids are substances that increase the concentration of hydrogen ions (H+) when dissolved in water.
Brønsted–Lowry Theory: In this theory, acids are defined as proton donors, which means they donate hydrogen ions (H+) to other substances.
Lewis Theory: Gilbert N. Lewis defined acids as electron pair acceptors, broadening the definition to include non proton donating substances.
Common Acids: Everyday acids include citric acid in citrus fruits, acetic acid in vinegar, and lactic acid in sour milk.
Industrial Acids: Sulfuric acid, nitric acid, and hydrochloric acid are widely used in industry for various applications.
pH Scale: The pH scale measures the acidity or basicity of a solution; acids have a pH less than 7.
Reactivity: Acids typically react with metals to produce hydrogen gas and with carbonates to produce carbon dioxide.
Neutralization: When acids react with bases, they form salt and water in a neutralization reaction.
Concentration: The strength of an acid is determined by its concentration and its ability to dissociate in water to produce hydrogen ions.
Acid Base Titration: This is a laboratory method used to determine the concentration of an acid or base in a solution using a neutralization reaction.
Buffer Solutions: These are solutions that resist changes in pH when small amounts of acid or base are added, important in many chemical and biological systems.
Examples of Acids:
Citric Acid: Found in citrus fruits like oranges and lemons.
Acetic Acid: The main component of vinegar.
Hydrochloric Acid: Present in gastric juice in the stomach.
Sulfuric Acid: Used in car batteries.
Phosphoric Acid: Used in soft drinks.
Characteristics of Acids:
Sour Taste: Acids typically have a sour taste.
pH Value: They have a pH less than 7.
Reactivity: React with metals to produce hydrogen gas.
Conductivity: Are electrolytes and can conduct electricity when dissolved in water.
Indicator Reaction: Change the color of indicators; for example, they turn blue litmus paper red.
Classification of Acids:
Based on Strength:
Strong Acids: Ionize completely in water (e.g., Hydrochloric acid).
Weak Acids: Do not ionize completely (e.g., Acetic acid).
Based on Composition:
Binary Acids: Contain hydrogen and one other element (e.g., HCl).
Oxyacids: Contain hydrogen, oxygen, and another element (e.g., H2SO4).
Uses of Acids:
Industrial: Sulfuric acid is used in the manufacture of fertilizers and in oil refining.
Food Industry: Citric acid is used as a preservative and flavoring agent.
Medicine: Acetylsalicylic acid (Aspirin) is used as a pain reliever.
Cleaning Agents: Hydrochloric acid is used in household cleaners to remove stains.
Importance of Acids :
Industrial Applications: Manufacturing fertilizers: Acids like nitric acid and sulfuric acid are used in producing fertilizers such as phosphate and ammonium nitrate.
Metal processing: Acids are involved in the pickling process to clean metal surfaces by reacting with the metal and releasing hydrogen gas.
Battery production: Sulfuric acid and other acids serve as electrolytes in batteries.
Organic synthesis: Carboxylic acids are essential in synthesizing esters.
Biological Functions: Digestion: Hydrochloric acid is a component of gastric juices in the stomach, aiding in breaking down complex molecules for absorption.
Genetic material: Nucleic acids, such as RNA and DNA, are vital for storing and transmitting genetic information.
Metabolism: Fatty acids are the basic units of fats, and amino acids are the building blocks of proteins in our bodies.
Food Industry: Flavoring: Citric acid is responsible for the sour taste in citrus fruits like lemons and oranges.
Preservation: Acetic acid is a major constituent of vinegar, used for preserving food.
Carbonation: Carbonic acid is formed when carbon dioxide is dissolved in beverages under high pressure, creating the fizz in soft drinks.
Catalysis: Esterification reactions: Strong acids like hydrochloric acid act as catalysts for esterification, avoiding saponification that can occur with base catalysts.
Biodiesel production: Brønsted acids are used to convert fats into biodiesel through transesterification.
Organic reactions: Lewis acids, such as metal crown ethers, facilitate aldol condensation reactions.
Environmental and Cleaning: Water treatment: Acids are used in adjusting pH levels and treating water to make it suitable for consumption and use.
Cleaning agents: Acids can be found in household cleaning products, effectively removing stains and buildups due to their corrosive nature.
