Bases
Introduction
Bases are substances that accept hydrogen ions (H⁺) or release hydroxide ions (OH⁻) in aqueous solutions.
They have a bitter taste, are slippery to touch, and turn red litmus blue.
In Bihar, bases are commonly used in agriculture, cleaning agents, and industrial processing.
Basic Properties of Bases
- Taste: Bitter
- Touch: Soapy/slippery
- pH: Above 7
- Litmus Test: Turns red litmus blue
- Conducts electricity in solution
- Reacts with acids → Neutralization reaction (forms salt + water)
📝 PYQ (BPSC): Base turns which litmus paper blue? → Red
📝 Expected MCQ: What is formed when base reacts with acid? → Salt and water
Common Examples of Bases
Strong Bases (completely ionize in water)
- Sodium hydroxide (NaOH) – caustic soda
- Potassium hydroxide (KOH) – caustic potash
- Calcium hydroxide (Ca(OH)₂) – lime water
- Magnesium hydroxide (Mg(OH)₂) – milk of magnesia
Weak Bases (partially ionize)
- Ammonium hydroxide (NH₄OH) – used in labs
- Copper hydroxide (Cu(OH)₂)
📝 Expected MCQ: Which is a weak base? → Ammonium hydroxide
Types of Bases
| Type | Description | Example |
|---|---|---|
| Alkalis | Soluble bases in water | NaOH, KOH, Ca(OH)₂ |
| Strong Bases | Completely dissociate into OH⁻ | NaOH, KOH |
| Weak Bases | Partially dissociate in solution | NH₄OH |
| Hydroxides | Contain OH⁻ ions | NaOH, Ca(OH)₂ |
📝 Expected MCQ: What are water-soluble bases called? → Alkalis
Uses of Bases (Bihar-Based Applications)
🧼 Cleaning Agents
- NaOH used in soap making in rural Bihar cottage industries
- Ca(OH)₂ (lime) used in whitewashing walls
- NH₄OH used in laboratories and textile units in Patna and Bhagalpur
🌾 Agriculture
- Slaked lime (Ca(OH)₂) used to neutralize acidic soil
- Bihar Agricultural Colleges test soil pH and recommend liming practices
🏥 Medical Use
- Milk of magnesia (Mg(OH)₂) used as antacid to relieve acidity
- Commonly available in rural Bihar health centers
🏗️ Industrial Use
- NaOH used in paper, rayon, detergent industries
- Bihar’s MSME sector uses bases in chemical processing
Base + Acid = Neutralization
- Reaction: Base + Acid → Salt + Water
- Example: NaOH + HCl → NaCl + H₂O
- Used in:
- Treating acid spills
- Correcting soil pH in Bihar farms
- Cleaning water in PHED projects
📝 PYQ (BPSC): What is formed in neutralization? → Salt and water
📝 Expected MCQ: Slaked lime is used for? → Soil pH neutralization
Safety and Handling
- Strong bases like NaOH are corrosive
- Can cause burns; use gloves, goggles in labs
- Store in airtight containers
- Neutralize spills using weak acids (e.g., vinegar)
📝 Expected MCQ: Which base is used in antacids? → Magnesium hydroxide
📝 Expected MCQ: Which base is corrosive and used in soaps? → Sodium hydroxide
PYQs + Expected MCQs
📝 PYQ (BPSC): What turns red litmus blue? → Base
📝 PYQ (CDPO): Which base is used in antacids? → Milk of magnesia
📝 Expected MCQ: What is an alkali? → Water-soluble base
📝 Expected MCQ: Slaked lime is which base? → Calcium hydroxide
📝 Expected MCQ: Which base is used in whitewashing? → Ca(OH)₂
📝 Expected MCQ: Which base is commonly used in making soap? → NaOH
Quick Revision Points
- Bases = bitter, slippery, pH > 7
- Red litmus → Blue
- Base + Acid → Salt + Water
- NaOH, KOH → strong bases
- NH₄OH → weak base
- Alkalis = water-soluble bases
- Bihar uses: soap making, whitewashing, soil treatment, antacids
Sources Used
- NCERT Class 7–10 Science
- Lucent GK – Chemistry Section
- Drishti Science Quick Book
- EduTeria & Ghatna Chakra PYQs (BPSC, CDPO)
- Bihar Agriculture Department – Soil Health Reports
- Bihar MSME & Cottage Industry Reports