Common Facts in Chemistry

Important Chemistry Facts

• Water: The universal solvent, chemical formula is H₂O.
• Air Composition: 78% Nitrogen, 21% Oxygen, 1% other gases.
• Atomic Number: Represents the number of protons in an atom.
• pH Scale: Ranges from 0 to 14; below 7 is acidic, 7 is neutral, above 7 is basic.
• Hydrogen: The lightest and most abundant element in the universe.
• Gold (Au): A noble metal, very unreactive and used in jewelry and electronics.
• Helium: Second lightest element, used in balloons and cooling superconductors.

Common Acids and Bases

• Hydrochloric Acid (HCl): Found in stomach, used in cleaning.
• Acetic Acid (CH₃COOH): Present in vinegar.
• Sulfuric Acid (H₂SO₄): Used in batteries and fertilizers.
• Sodium Hydroxide (NaOH): Used in soap making, also called caustic soda.
• Calcium Hydroxide (Ca(OH)₂): Known as limewater.

Periodic Table Quick Facts

• First element: Hydrogen (H)
• Lightest metal: Lithium (Li)
• Most reactive metal: Francium (Fr)
• Most reactive non-metal: Fluorine (F)
• Alkali metals: Group 1 elements
• Noble gases: Group 18 elements, inert in nature

Useful Exam Tips

• Remember OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).
• Common salt is Sodium Chloride (NaCl).
• Rusting is a chemical change involving Iron + Oxygen + Water → Rust.
• Molecules are two or more atoms chemically bonded (e.g., O₂, H₂O).
• Elements are pure substances consisting of only one type of atom.

Conclusion

These common facts serve as a quick revision guide to some of the most fundamental concepts in chemistry. They are frequently asked in various competitive exams and are key to building a strong foundation in the subject.