Chemical compounds are substances formed by the chemical combination of two or more elements in a fixed proportion by mass. Unlike mixtures, the constituents of a compound lose their individual properties, giving rise to a new substance with unique chemical and physical characteristics.
Types of Chemical Compounds
Chemical compounds are broadly classified based on the nature of their chemical bonds and their origin.
Ionic Compounds
These compounds are formed by the complete transfer of electrons from a metal to a non-metal, resulting in the formation of cations and anions held together by strong electrostatic forces.
- Characteristics: High melting and boiling points, soluble in water, and conduct electricity in molten or aqueous states.
- Examples: Sodium Chloride (NaCl), Magnesium Oxide (MgO), Calcium Chloride (CaCl2).
Covalent Compounds
These compounds are formed by the sharing of electrons between non-metal atoms to achieve a stable electronic configuration.
- Characteristics: Relatively low melting and boiling points, generally insoluble in water (but soluble in organic solvents), and non-conductors of electricity.
- Examples: Carbon Dioxide (CO2), Methane (CH4), Water (H2O).
Coordinate (Dative) Compounds
A subtype of covalent compounds where the shared pair of electrons is contributed by only one of the combining atoms (the donor) to the other (the acceptor).
- Examples: Ammonium ion (NH4^+), Hydronium ion (H3O^+).
Organic vs. Inorganic Compounds
- Organic Compounds: Compounds primarily containing carbon covalently bonded to hydrogen, oxygen, nitrogen, and other non-metals. (Examples: Carbohydrates, proteins, hydrocarbons).
- Inorganic Compounds: Compounds originating from non-living mineral sources, encompassing oxides, carbonates, and halides. (Examples: Rocks, minerals, salts).
Major Chemical Compounds in Daily Use and Industry
The following table details key chemical compounds, their common names, chemical formulas, and primary applications relevant to competitive examinations.
| Common Name | Chemical Name | Chemical Formula | Key Applications and Industrial Uses |
| Baking Soda | Sodium Bicarbonate | NaHCO3 | Used in baking, antacids, and fire extinguishers. |
| Washing Soda | Sodium Carbonate Decahydrate | Na2CO3 · 10H2O | Used in glass manufacture, water softening, and laundry. |
| Bleaching Powder | Calcium Oxychloride | CaOCl2 | Disinfectant for water, bleaching agent in textiles. |
| Plaster of Paris | Calcium Sulfate Hemihydrate | CaSO4 · 1/2H2O | Used in bone fracturing casts, statues, and false ceilings. |
| Gypsum | Calcium Sulfate Dihydrate | CaSO4 · 2H2O | Used in cement manufacturing to retard setting time. |
| Caustic Soda | Sodium Hydroxide | NaOH | Used in soap making, paper pulp, and petroleum refining. |
| Quicklime | Calcium Oxide | CaO | Used in manufacturing cement, glass, and purification of sugar. |
| Slaked Lime | Calcium Hydroxide | Ca(OH)2 | Used in whitewashing, sewage treatment, and soil neutralization. |
| Laughing Gas | Nitrous Oxide | N2O | Used as an anesthetic in dentistry and a propellant. |
| Epsom Salt | Magnesium Sulfate Heptahydrate | MgSO4 · 7H2O | Used in agriculture to correct magnesium deficiency, bath salts. |
| Blue Vitriol | Copper Sulfate Pentahydrate | CuSO4 · 5H2O | Used as a fungicide (Bordeaux mixture) and electroplating. |
| Green Vitriol | Iron(II) Sulfate Heptahydrate | FeSO4 · 7H2O | Used in treating iron deficiency anemia and ink manufacturing. |
Environmental and Industry-Specific Compounds
Greenhouse Gases and Atmospheric Compounds
- Carbon Dioxide (CO2): Primary greenhouse gas driven by fossil fuel combustion; utilized in solid form as “Dry Ice” for refrigeration without melting.
- Methane (CH4): Major component of Compressed Natural Gas (CNG) and Biogas; possesses a higher global warming potential than carbon dioxide.
- Sulfur Dioxide (SO2) and Nitrogen Dioxide (NO2): Industrial pollutants responsible for acid rain through the formation of H2SO4 and HNO3 in the atmosphere.
Agricultural and Industrial Compounds
- Urea (NH2CONH2): The first organic compound synthesized in a laboratory from an inorganic starting material (by Friedrich Wöhler). It is the most widely used nitrogenous fertilizer.
- Ammonia (NH3): Produced industrially via the Haber-Bosch Process; serves as the precursor for nitrogenous fertilizers and explosives.
- Phosphoric Acid (H3PO4): Used in production of triple superphosphate fertilizers and as an acidulant in cola beverages.
High-Yield Prelims Trivia and Conceptual Facts
Water of Crystallization
Many compounds contain a fixed number of water molecules chemically combined in definite proportions per formula unit.
- Heating Copper Sulfate Pentahydrate (Blue) drives off water, turning it into Anhydrous Copper Sulfate (White).
- Plaster of Paris converts back into Gypsum upon mixing with water, an exothermic reaction that sets into a hard mass.
Hardness of Water Compounds
- Temporary Hardness: Caused by the presence of dissolved Bicarbonates of Calcium and Magnesium (Ca(HCO3)2 and Mg(HCO3)2). It can be removed simply by boiling.
- Permanent Hardness: Caused by the presence of Sulfates and Chlorides of Calcium and Magnesium (CaCl2, MgSO4, etc.). It requires chemical treatment like the Permutit method or Calgon process.
Common Acid-Base Indicators
- Litmus: A natural dye extracted from Lichens. It turns red in acidic solutions and blue in basic solutions.
- Phenolphthalein: Synthetic indicator that remains colorless in acidic solutions but turns deep pink in basic solutions.
- Methyl Orange: Turns red in acidic mediums and yellow in basic mediums.