Acids, Bases and Salts

Comprehensive Learning Module for Grade 9-10 Students

📚 Educational Videos

🔬 Fundamental Definitions

Acids

Definition: Substances that release hydrogen ions (H⁺) when dissolved in water

Origin: The word "acid" comes from Latin 'acere' meaning sour

Ion Release: H⁺ ions are responsible for acidic properties

Bases

Definition: Substances that release hydroxide ions (OH⁻) or accept hydrogen ions

Alkalis: Water-soluble bases are called alkalis

Ion Release: OH⁻ ions are responsible for basic properties

Salts

Definition: Ionic compounds formed from acid-base neutralization reactions

Composition: Positive ions (cations) from bases and negative ions (anions) from acids

Neutrality: Generally neutral with pH around 7

📊 Physical Properties

Property Acids Bases Salts
Taste Sour (like lemon juice) Bitter Varies (mostly salty)
Feel/Touch Normal Slippery/Soapy Normal
Color Mostly colorless (H₂SO₄ can be yellow due to impurities) Colorless except Fe and Cu hydroxides Variable colors
Solubility Generally soluble in water Some soluble (alkalis), some not Variable solubility
Electrical Conductivity Good conductors in aqueous solution Good conductors in aqueous solution Conduct when dissolved
Litmus Test Turn blue litmus red Turn red litmus blue No effect on litmus
pH Range 0 - 6.9 (less than 7) 7.1 - 14 (greater than 7) Around 7 (neutral)

⚗️ Chemical Properties & Reactions

🔥 Reactions of Acids

1. Acid + Metal → Salt + Hydrogen Gas

Zn + H₂SO₄ → ZnSO₄ + H₂ ↑

Example: Zinc reacts with dilute sulphuric acid to produce zinc sulphate and hydrogen gas

Test: Hydrogen gas produces a 'pop' sound when ignited

2. Acid + Metal Carbonate → Salt + Water + Carbon Dioxide

2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂ ↑

Observation: Brisk effervescence (bubbling) due to CO₂ release

Test: CO₂ turns lime water milky

3. Acid + Metal Hydrogen Carbonate → Salt + Water + Carbon Dioxide

HCl + NaHCO₃ → NaCl + H₂O + CO₂ ↑

Example: Hydrochloric acid with baking soda produces effervescence

4. Acid + Metal Oxide/Hydroxide → Salt + Water

CuO + 2HCl → CuCl₂ + H₂O

Note: This is a neutralization reaction

5. Acid + Base → Salt + Water (Neutralization)

HCl + NaOH → NaCl + H₂O

Universal Reaction: The most important acid-base reaction

🧪 Reactions of Bases

1. Base + Metal → Salt + Hydrogen Gas

2NaOH + Zn → Na₂ZnO₂ + H₂ ↑

Example: Sodium hydroxide heated with zinc produces sodium zincate and hydrogen

2. Base + Non-metal Oxide → Salt + Water

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Example: Lime water with carbon dioxide forms calcium carbonate

🌍 Real-World Uses and Applications

🍋 Common Acids in Daily Life

Citric Acid

Found in oranges, lemons, and other citrus fruits. Used as food preservative and flavor enhancer

Acetic Acid

Main component of vinegar (5-8%). Used in cooking, food preservation, and cleaning

Lactic Acid

Found in milk and yogurt. Produced during muscle fatigue. Used in food industry

Hydrochloric Acid

Present in stomach gastric juice for digestion. Industrial use in metal cleaning

Sulfuric Acid

Used in car batteries, fertilizer production, and petroleum refining

Tartaric Acid

Found in tamarind and grapes. Used in baking powder and wine making

🧼 Common Bases in Daily Life

Sodium Hydroxide (NaOH)

Used in soap making, drain cleaners, and paper industry

Magnesium Hydroxide

Milk of magnesia - used as antacid for treating indigestion

Calcium Hydroxide

Lime water used in whitewashing walls and water treatment

Ammonium Hydroxide

Used in household cleaning liquids and window cleaners

Potassium Hydroxide

Used in bathing soaps and industrial processes

Baking Soda (NaHCO₃)

Used in cooking, baking, antacid medicine, and fire extinguishers

🧂 Salts and Their Applications

Sodium Chloride (NaCl)

Table salt for flavoring food, food preservation, and de-icing roads

Calcium Carbonate (CaCO₃)

Used in cement, toothpaste, and as dietary supplement

Magnesium Sulfate

Epsom salt used as laxative and in bath soaks for muscle relief

Potassium Sulfate

Used as fertilizer in agriculture

Sodium Fluoride

Added to toothpaste and water for dental health

Borax (Na₂B₄O₇)

Used as cleaning agent and water softener

💊 Medical and Health Applications

🏭 Industrial Applications

🌿 Environmental Applications

🧠 Interactive Flashcards

Click on each card to reveal the answer!

What are H⁺ ions and why are they important?
H⁺ ions are hydrogen ions released by acids in solution. They determine acidity and pH level - more H⁺ ions mean lower pH and stronger acid
What happens when zinc reacts with hydrochloric acid?
Zn + 2HCl → ZnCl₂ + H₂ ↑
Zinc chloride salt is formed and hydrogen gas is released with a 'pop' sound
Name the gas released when acid reacts with metal carbonate
Carbon dioxide (CO₂) gas is released with brisk effervescence. It turns lime water milky when passed through it
What makes bases feel slippery?
OH⁻ (hydroxide) ions make bases feel slippery or soapy. This is a characteristic physical property of bases
Why is neutralization important in daily life?
Neutralization helps treat indigestion (antacids), bee stings (baking soda), soil pH balance, and industrial waste treatment
What is the pH of a strong acid like HCl?
Strong acids like HCl have pH between 0-2. The lower the pH, the stronger the acid
Give an example of acid + base neutralization
HCl + NaOH → NaCl + H₂O
Hydrochloric acid + Sodium hydroxide → Salt + Water
Why does lemon juice taste sour?
Lemon juice contains citric acid which releases H⁺ ions. These hydrogen ions give the characteristic sour taste
What is an alkali?
An alkali is a water-soluble base. Examples include NaOH, KOH, and Ca(OH)₂. All alkalis are bases but not all bases are alkalis
How do indicators work?
Indicators change color in acidic vs basic solutions. Blue litmus turns red in acids, red litmus turns blue in bases
What happens when CO₂ is passed through lime water?
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
Lime water turns milky due to formation of calcium carbonate precipitate
Why is baking soda used in fire extinguishers?
When heated, NaHCO₃ releases CO₂ gas which displaces oxygen and helps extinguish fires

📊 Concept Diagrams

pH Scale and Common Substances

flowchart LR A[pH 0-1
Battery Acid
Very Strong Acid] --> B[pH 2-3
Lemon Juice
Vinegar
Strong Acid] B --> C[pH 4-5
Coffee
Tomatoes
Weak Acid] C --> D[pH 6
Milk
Urine
Mild Acid] D --> E[pH 7
Pure Water
Blood
Neutral] E --> F[pH 8
Seawater
Baking Soda
Mild Base] F --> G[pH 9-10
Soap
Milk of Magnesia
Base] G --> H[pH 11-12
Household Ammonia
Strong Base] H --> I[pH 13-14
Drain Cleaner
Very Strong Base] style A fill:#ff0000,color:#fff style B fill:#ff4444,color:#fff style C fill:#ff8888,color:#fff style D fill:#ffcccc,color:#000 style E fill:#88ff88,color:#000 style F fill:#ccffcc,color:#000 style G fill:#4488ff,color:#fff style H fill:#0044ff,color:#fff style I fill:#0000ff,color:#fff

Acid-Base Reaction Types

--- config: theme: redux-color --- mindmap root((Acid-Base Reactions)) (Acid + Metal) "Salt + Hydrogen Gas" "Zn + 2HCl → ZnCl₂ + H₂" "Pop sound test" (Acid + Carbonate) "Salt + Water + Carbon Dioxide" "Effervescence observed" "Lime water test" (Acid + Base) "Salt + Water" "Neutralization reaction" "Universal reaction" (Base + Metal) "Salt + Hydrogen Gas" "Zn + 2NaOH → Na₂ZnO₂ + H₂" "Heat required" (Base + Non-metal Oxide) "Salt + Water" "Ca#40;OH#41;₂ + CO₂ → CaCO₃ + H₂O" "Lime water turns milky"

Applications in Daily Life

graph LR A[Acids, Bases & Salts in Daily Life] --> B[Food & Kitchen] A --> C[Health & Medicine] A --> D[Cleaning & Hygiene] A --> E[Industry] A --> F[Agriculture] B --> B1[Vinegar - Acetic Acid] B --> B2[Citrus Fruits - Citric Acid] B --> B3[Baking Soda - Leavening] B --> B4[Salt - Food Flavoring] C --> C1[Antacids - Stomach Relief] C --> C2[Vitamin C - Immune System] C --> C3[Epsom Salt - Muscle Relief] C --> C4[Fluoride - Dental Care] D --> D1[Soap - NaOH Based] D --> D2[Bleach - Disinfectant] D --> D3[Ammonia - Glass Cleaner] D --> D4[Lime - Whitewashing] E --> E1[Batteries - H₂SO₄] E --> E2[Metal Cleaning - HCl] E --> E3[Paper Making - NaOH] E --> E4[Fertilizers - Various Salts] F --> F1[Soil pH - Lime Treatment] F --> F2[Fertilizers - NPK Salts] F --> F3[Pesticides - Various Compounds] style A fill:#e1f5fe style B fill:#fff3e0 style C fill:#f3e5f5 style D fill:#e8f5e8 style E fill:#fff8e1 style F fill:#fce4ec

🎮 pH Scale Interactive Game

Drag and drop substances to their correct position on the pH scale!

0-1
Very Acidic
2-3
Acidic
4-5
Weak Acid
6
Mild Acid
7
Neutral
8
Mild Base
9-10
Base
11-12
Strong Base
13-14
Very Strong

Drag these substances to their correct pH range:

Lemon Juice
Pure Water
Baking Soda
Battery Acid
Household Ammonia
Coffee
Seawater
Drain Cleaner
Vinegar
Milk of Magnesia
Score: 0/10

🧪 3D Static Molecular Models

Controls: Left Click + Drag to Rotate | Right Click + Drag to Pan | Mouse Wheel to Zoom

📝 Knowledge Assessment

1. What ion do acids release in aqueous solution?

A) OH⁻ ions
B) H⁺ ions
C) Na⁺ ions
D) Cl⁻ ions

2. What gas is produced when zinc reacts with hydrochloric acid?

A) Oxygen
B) Carbon dioxide
C) Hydrogen
D) Nitrogen

3. Which gas is released when acid reacts with metal carbonate?

A) Hydrogen
B) Carbon dioxide
C) Oxygen
D) Nitrogen

4. What happens when carbon dioxide is passed through lime water?

A) It turns milky
B) It turns blue
C) It turns red
D) No change occurs

5. Which of the following is NOT a physical property of bases?

A) Bitter taste
B) Slippery feel
C) Turn red litmus blue
D) React with metals to produce hydrogen

6. What is the chemical name of baking soda?

A) Sodium carbonate
B) Sodium chloride
C) Sodium hydrogen carbonate
D) Sodium hydroxide

7. Which acid is found in vinegar?

A) Citric acid
B) Acetic acid
C) Lactic acid
D) Hydrochloric acid

8. What type of reaction occurs when an acid neutralizes a base?

A) Neutralization reaction
B) Decomposition reaction
C) Synthesis reaction
D) Displacement reaction

9. Which substance is used to treat acidic soil?

A) Sulfuric acid
B) Hydrochloric acid
C) Calcium hydroxide (lime)
D) Sodium chloride

10. What is the pH range of strong acids?

A) 7-8
B) 0-2
C) 12-14
D) 6-7
Quiz Score: 0/10

⚗️ Important Compounds

Important Compounds and Their Uses

mindmap root((Important Compounds)) Sodium Hydroxide Soap Making Paper Industry Drain Cleaners Metal Processing Bleaching Powder Water Disinfection Textile Bleaching Swimming Pools Odor Removal Baking Soda Cooking & Baking Antacid Medicine Fire Extinguisher Cleaning Agent Washing Soda Laundry Detergent Water Softener Glass Making pH Buffer Plaster of Paris Medical Casts Construction Art & Sculpture Dental Molds

📋 Detailed Information

Compound Chemical Formula Preparation Main Uses Properties
Sodium Hydroxide
(Caustic Soda)
NaOH Electrolysis of brine:
2NaCl + 2H₂O → 2NaOH + H₂ + Cl₂
Soap making, paper industry, petroleum refining, drain cleaners Highly caustic, deliquescent, strong base (pH ~14)
Bleaching Powder Ca(OCl)₂ Chlorine gas + dry slaked lime:
Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O
Water purification, textile bleaching, disinfectant, swimming pools Releases chlorine, strong oxidizing agent, unstable in light
Baking Soda
(Sodium Bicarbonate)
NaHCO₃ Solvay process:
Na₂CO₃ + H₂O + CO₂ → 2NaHCO₃
Baking (leavening), antacid, fire extinguisher, cleaning Mild base, releases CO₂ when heated, slightly alkaline
Washing Soda
(Sodium Carbonate)
Na₂CO₃·10H₂O Heating baking soda:
2NaHCO₃ → Na₂CO₃ + H₂O + CO₂
Laundry detergent, water softener, glass making, pH adjustment Strong base, efflorescent, removes hardness of water
Plaster of Paris CaSO₄·½H₂O Heating gypsum at 373K:
CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O
Medical casts, construction, decorative items, dental molds Sets quickly with water, becomes hard, slightly soluble

🔬 Key Preparation Reactions

Sodium Hydroxide:
2NaCl + 2H₂O → 2NaOH + H₂ + Cl₂ (Electrolysis of brine)
Bleaching Powder:
Ca(OH)₂ + Cl₂ → Ca(OCl)₂ + H₂O (Chlorine + Slaked lime)
Baking Soda:
Na₂CO₃ + H₂O + CO₂ → 2NaHCO₃ (Solvay process)
Washing Soda:
2NaHCO₃ → Na₂CO₃ + H₂O + CO₂ (Heating baking soda)
Plaster of Paris:
CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O (Heating gypsum at 373K)

💡 Important Applications and Facts

  • Sodium Hydroxide is extremely caustic and can cause severe chemical burns. It's essential in soap making through saponification process
  • Bleaching Powder acts as both bleaching agent and disinfectant due to chlorine release. It loses potency when exposed to air and light
  • Baking Soda releases CO₂ when heated or reacts with acids, making it perfect for baking and fire extinguishing
  • Washing Soda removes permanent hardness of water by precipitating calcium and magnesium salts
  • Plaster of Paris sets by combining with water to reform gypsum, creating a hard, moldable material perfect for medical casts

🏭 Industrial and Commercial Significance

  • Economic Impact: These compounds form the backbone of many industrial processes, from textile manufacturing to construction
  • Safety Considerations: Proper handling is crucial - NaOH and bleaching powder require special storage and safety equipment
  • Environmental Role: Used in water treatment, waste management, and pollution control applications
  • Medical Applications: From antacids (NaHCO₃) to emergency medical casts (Plaster of Paris), these compounds save lives daily