Definitions [3]
Define catalytic hydrogenation.
catalytic hydrogenation is a process by which hydrogen gas is passed through vegetable oils in the presence of catalyst like Ni, Pt or Pd to convert them into solid vanaspati ghee.
Definition: Hydrogen
Hydrogen is the first and lightest element in the periodic table. It is the most abundant element in the universe, constituting about 70% of the total mass of the universe and 91% of total atoms.
Definition: Alkali Metals
The Group 1 elements (Li, Na, K, Rb, Cs, Fr) are collectively called alkali metals. All elements except Hydrogen in this group are called alkali metals.
Key Points
Key Points: Hydrogen
- Electronic configuration: 1s¹ — it exists as a diatomic molecule H₂ called dihydrogen.
- Hydrogen does not belong to any group definitively; it resembles both alkali metals (loses 1 electron) and halogens (gains 1 electron).
- Alkali metals have oxidation number +1, and alkaline earth metals have oxidation number +2 in all their compounds.
Isotopes of Hydrogen:
| Isotope | Symbol | Atomic Number (Z) | Atomic Mass (A) | Natural Abundance |
|---|---|---|---|---|
| Protium |
\[_1^1HorH\] |
1 | 1 | 99.98% (naturally occurring) |
| Deuterium | \[_1^2HorD\] | 1 | 2 | 0.02% (naturally occurring) |
| Tritium | \[_1^3HorT\] | 1 | 3 | Trace (radioisotope) |
Uses of Hydrogen:
- Hydrogenation of oils to convert them into solid fats (Vanaspati ghee)
- Liquid dihydrogen is used as a rocket fuel
- Production of ammonia (Haber process)
- In production of methanol (from CO)
Key Points: Alkali Metals
Electronic Configurations:
| Period | Element | Symbol | Atomic No. | Electronic Configuration |
|---|---|---|---|---|
| 2 | Lithium | Li | 3 | [He] 2s¹ |
| 3 | Sodium | Na | 11 | [Ne] 3s¹ |
| 4 | Potassium | K | 19 | [Ar] 4s¹ |
| 5 | Rubidium | Rb | 37 | [Kr] 5s¹ |
| 6 | Caesium | Cs | 55 | [Xe] 6s¹ |
| 7 | Francium | Fr | 87 | [Rn] 7s¹ |
Periodic Trends in Group 1
| Property | Trend Down the Group |
|---|---|
| Atomic radius | Increases |
| Ionic radius | Increases |
| Density | Irregular trend |
| Ionisation enthalpy | Decreases (lower IE → more reactive) |
| Melting point | Decreases |
Biological Importance
- Na⁺ ions participate in the transmission of nerve signals
- High concentration of Na⁺ and low concentration of K⁺ is found in blood plasma
- High concentration of K⁺ and low concentration of Na⁺ is found inside human cells
- K⁺ ions are essential for nerve impulse transmission and maintaining osmotic balance
Uses of Alkali Metals
- Lithium is used in lithium-ion batteries
- Potassium is used in manufacturing potassium superoxide (KO₂) for oxygen generation in submarines, mountaineering, and space equipment
- Potassium chloride is used as a fertilizer
- Be is used as a moderator in nuclear reactors
Key Points: Some Important Compounds of Elements of S-block
| Compound | Preparation (Easy) | Properties (Easy) | Uses |
|---|---|---|---|
| Sodium carbonate (Na₂CO₃·10H₂O) (Washing soda) | Prepared by Solvay process: NH₃ + CO₂ + H₂O → NaHCO₃ → Na₂CO₃ | White crystalline solid; loses water on heating (efflorescent) | Used in making soap, water softening, cleaning |
| Sodium hydroxide (NaOH) | Prepared by electrolysis of NaCl solution (Castner-Kellner process) | White solid; highly soluble; strongly basic; absorbs moisture (deliquescent) | Used in petroleum refining and purification of bauxite |
| Calcium carbonate (CaCO₃) | Formed when CO₂ is passed through Ca(OH)₂ solution | Soft white solid; insoluble in water | Used in building material; making quicklime (CaO) |
| Hydrogen peroxide (H₂O₂) | Prepared from BaO₂ + H₂SO₄ → H₂O₂ | Acts as oxidizing and reducing agent; miscible with water | Used as antiseptic, mouthwash, bleaching agent |
| Lithium aluminium hydride (LiAlH₄) | Prepared by reaction: LiH + AlCl₃ → LiAlH₄ | Colourless solid; reacts violently with water | Used as strong reducing agent; preparation of PH₃ |
