Echoes Within

Here is a summary note for MCQ preparation for the lesson:
“General and Language of Chemistry”
(Covers: Atoms, Ions, Molecules, Elements, Compounds, Radicals, Valency, Commercial names of compounds, Types of Chemical Reaction, Methods of Mixture Separation)

1. Atom, Molecule, Ion

• Atom: The smallest unit of an element that retains its properties. Eg: H, O, Na.

• Molecule: A Combination of two or more atoms (same or different). Eg: O₂, H₂O.

• Ion: Charged particles.

  • Cation: Positively charged (Na⁺, Ca²⁺)

  • Anion: Negatively charged (Cl⁻, SO₄²⁻)

2. Element and Compound

• Element: Pure substance made of only one type of atom. Eg: Iron (Fe), Oxygen (O₂).

• Compound: Substance formed by the chemical combination of two or more elements in a fixed proportion. Eg: H₂O, NaCl.

• Molecule of Element: O₂, H₂

• Molecule of Compound: CO₂, NH₃

3. Radical and Valency

• Radical: A Group of atoms that behaves like a single atom in chemical reactions. Can be positive or negative.

  • Eg: OH⁻, SO₄²⁻, NH₄⁺

• Valency: The Combining capacity of an atom or radical.

  • Eg: H (1), O (2), N (3), C (4), SO₄ (2), Cl (1)

4. Naming Compounds (Commercial Names)

• H₂O – Water

• NaCl – Table salt

• CaCO₃ – Limestone/Marble/Chalk

• NaHCO₃ – Baking soda

• Ca(OH)₂ – Lime water

• Na₂CO₃ – Washing soda

• HCl – Hydrochloric acid (muriatic acid)

5. Types of Chemical Reactions

• Combination Reaction: A + B → AB

• Decomposition Reaction: AB → A + B

• Displacement Reaction: A + BC → AC + B

• Double Displacement Reaction: AB + CD → AD + CB

• Neutralization: Acid + Base → Salt + Water

• Combustion: Fuel + O₂ → CO₂ + H₂O + Heat

6. Methods of Separation of Mixtures

• Evaporation: For salt from saltwater

• Filtration: Insoluble solids from liquids

• Distillation: Separating two miscible liquids

• Decantation: Solid-liquid separation after sedimentation

• Centrifugation: Fine solid particles from liquid

• Sublimation: Separating a solid that sublimes (e.g., camphor, iodine)

• Chromatography: Separation of different dyes/pigments

• Magnetic Separation: Iron from a mixture

🧠 Tips for MCQs:

• Know the symbols and formulas well.

• Be clear about valency rules and how to write chemical formulas.

• Identify radicals and their charges quickly.

• Remember the types and examples of chemical reactions.

• Understand practical methods of separation with suitable examples.