Acids
Basic chemistry concepts about acids. Types of acids, properties, pH value and important acids for TNPSC exams.
Learning Content
🧪 Acids - Introduction!
Acid = Compound that gives H⁺ ion | Sour taste pH < 7
📊 Types of Acids - MASTER TABLE
| Type | Explanation | Example |
|---|---|---|
| Mineral acids | from minerals | HCl, H₂SO₄, HNO₃ |
| Organic acids | from organisms | Acetic, citric, lactic |
| A strong acid | It is completely ionic | HCl, H₂SO₄, HNO₃ |
| Dilute acid | is partially ionic | CH₃COOH, H₂CO₃ |
⚗️ Major mineral acids
| acid | formula | Another name | benefit |
|---|---|---|---|
| Hydrochloric | HCl | Hydrochloric acid, muriatic | Stomach digestion |
| Sulfuric | H₂SO₄ | King of Acids | Battery, Fertilizer |
| Nitric | HNO₃ | Aqua Fortis | Fertilizer, explosives |
| Organic | H₂CO₃ | - | Soda drinks |
| Phosphoric | H₃PO₄ | - | Fertilizer, food |
🎯 Acidic properties
- 😋 Sour taste
- 🔵 Turns blue litmus red
- ⚡ Electrically conductive
- 🔥 H₂ gas with metal
- 💧 Salt + water along with alkali
🍋 Organic Acids & Sources!
Acids found in living organisms in nature
📊 Acid - by MASTER TABLE
| acid | formula | By |
|---|---|---|
| Citric acid | C₆H₈O₇ | 🍋 Lemon, orange |
| Acetic acid | CH₃COOH | 🫙 Vinegar (Kadi) |
| Tartaric acid | C₄H₆O₆ | 🍇 Grapes, tamarind |
| Oxalic acid | C₂H₂O₄ | 🥬 Tomato, spinach |
| Lactic acid | C₃H₆O₃ | 🥛 Curd, fermented milk |
| Malic acid | C₄H₆O₅ | 🍎 Apple |
| Formic acid | HCOOH | 🐜 Ant bite |
| Uric acid | C₅H₄N₄O₃ | 💧 Urine |
| Ascorbic acid | C₆H₈O₆ | 🍊 Gooseberry (Vit C) |
| Oleic acid | C₁₈H₃₄O₂ | 🫒 Olive oil |
| Stearic acid | C₁₈H₃₆O₂ | 🧈 fat |
💡 QUICK MEMORY - "Elushi Thala"
ALime = citric
Lu= Tamarind = Tartaric
CUrine = Uric
ThaYir = lactic
La= Apple = Malik
📊 pH Value & Indicators!
pH = measure of acidity/alkaline | 0-14 scale
🎯 pH scale
| pH 0-6 | acid | more H⁺ |
| pH 7 | Neutral | pure water |
| pH 8-14 | alkaline | OH⁻ is more |
📋 pH value of materials
| Meaning | pH | Character |
|---|---|---|
| Stomach acid (HCl) | 1-2 | A strong acid |
| Lemon juice | 2-3 | acid |
| Vinegar | 2.5-3 | acid |
| tomato | 4 | Dilute acid |
| Milk | 6.5 | Dilute acid |
| pure water | 7 | Neutral |
| the blood | 7.35-7.45 | Slightly salty |
| Baking soda | 8.5 | alkaline |
| Soap | 9-10 | alkaline |
| Ammonia | 11 | Strong alkali |
| Lime water | 12 | Strong alkali |
🔬 Indicators
| indicator | in acid | in alkali |
|---|---|---|
| Litmus | 🔴 Red | 🔵 Blue |
| Methyl orange | 🔴 Red | 🟡 Yellow |
| Phenolphthalein | ⚪ Colorless | 🩷 Pink |
| Turmeric | 🟡 Yellow | 🔴 Red |
📝 TNPSC Main Questions & Shortcuts!
🎯 Frequently Asked Questions
| Q: King of Acids? | ✅ H₂SO₄ (sulfuric acid) |
| Q: Stomach acid? | ✅ HCl (Hydrochloric) |
| Q: Acid in lemons? | ✅ Citric acid |
| Q: Acid in curd? | Lactic acid |
| Q: Acid in vinegar? | Acetic acid (CH₃COOH) |
| Q: Acid in ant bites? | ✅ Formic acid |
| Q: What if the pH is 7? | ✅ Neutral |
| Q: Blood pH? | ✅ 7.35 - 7.45 |
| Q: What is Aqua Regia? | ✅ HCl + HNO₃ (3:1) – dissolves gold |
| Q: Reddening blue litmus? | ✅ Acid |
💡 SUPER SHORTCUTS
🔴 3 Strong Acids:
HCl, H₂SO₄, HNO₃
💡 "H-H-H" (H-H-H)
🔵 Acid + Base:
Salt + water
💡 Neutralization
🎯 Acid - by QUICK MATCH
| 🍋 Lemon | Citric |
| 🥛 Yogurt | Lactic |
| 🫙 Vinegar | Acetic |
| 🍎 Apple | Malik |
| 🍇 grapes | Tartaric |
| 🐜 Ant | Formic |
| 🥬 Tomatoes | Oxalic |
| 🍊 Gooseberry | Ascorbic (Vit C) |
📋 pH memory TRICK
🎯pH < 7 = acid(Acid - Sour)
🎯pH = 7 = neutral(Pure Water)
🎯pH > 7 = alkaline(Base - bitter)
💡"Blood 7.4"- Slightly salty!
💡"Stomach 1-2"- Very acid!
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