🧪 Chapter 2 – Acids, Bases and Salts (Karnataka SSLC Science, 2024–25)


🧪 Chapter 2 – Acids, Bases and Salts

(Karnataka SSLC Science, 2024–25)





🌿 1. What are Acids and Bases?

Type Definition Example
Acid     Substance that gives
    H⁺ ions in water		         HCl, H₂SO₄
Base     Substance that gives
    OH⁻ ions in water		         NaOH, KOH
Salt     Formed when acid
     reacts with base		         NaCl, CaSO₄

👉 Acid + Base → Salt + Water (Neutralisation reaction)
Example: HCl + NaOH → NaCl + H₂O

🗣️ Kannada: ಅಮ್ಲ + ಕ್ಷಾರ → ಉಪ್ಪು + ನೀರು

🌈 2. Indicators

They show whether a substance is an acid or a base.

Indicator In Acid In Base
Litmus paper     Red  Blue
Phenolphthalein     Colourless     Pink
Methyl orange     Red Yellow

🧠 Tip: Litmus changes blue → red in acid.
Acid = Red, Base = Blue (👉 Remember “A R B B”)

⚗️ 3. Chemical Reactions of Acids and Bases

Reaction Example Type
Acid + Metal
 → Salt + H₂
     Zn + H₂SO₄ → ZnSO₄ + H₂     Displacement
Acid + Metal Carbonate    
 → Salt + H₂O + CO₂
     CaCO₃ + HCl → CaCl₂ + H₂O + CO₂     Double displacement
Base + Acid
→ Salt + Water
     NaOH + HCl → NaCl + H₂O     Neutralisation

🧊 4. pH Scale

The pH scale measures how acidic or basic a solution is.
👉 Range: 0 – 14

pH Range     Nature Example
0–7     Acidic     Lemon juice (pH ≈ 2)
7         Neutral     Pure water
7–14     Basic     Soap (pH ≈ 10)

🧠 Tip:

  • Smaller pH = Strong acid

  • Larger pH = Strong base

🗣️ Kannada: pH ಮೌಲ್ಯ ಕಡಿಮೆ → ಅಮ್ಲ ಹೆಚ್ಚು , pH ಮೌಲ್ಯ ಹೆಚ್ಚು → ಕ್ಷಾರ ಹೆಚ್ಚು

🧪 5. Importance of pH in Daily Life

Situation Explanation
Tooth decay         Bacteria make mouth acidic (pH < 5.5).
Use toothpaste (basic) to neutralize.
Antacid tablets         Contain base to neutralize extra acid in stomach.
Soil treatment     If soil is too acidic → add lime (Ca(OH)₂).
Bee sting     Acidic poison → apply baking soda (base).
Wasp sting     Basic poison → apply vinegar (acid).

🧂 6. Important Salts and Their Uses

Salt Formula Uses
Common salt     NaCl Food, raw material for chemicals
Baking soda         NaHCO₃ Baking, antacid
Washing soda     Na₂CO₃·10H₂O     Laundry, glass making
Bleaching powder     CaOCl₂ Disinfectant, making paper white
Plaster of Paris         CaSO₄·½H₂O Used for casts and decoration

🌡️ 7. Chloro–Alkali Process

When NaCl solution is electrolysed →
produces NaOH, Cl₂ & H₂.

Product Use
NaOH Soap, detergent
Cl₂ Disinfectant, PVC
H₂ Fuel, making ammonia

🔥 8. Exam Practice Questions

🔹 1 Mark

  1. What is an acid?

  2. Write one property of base.

  3. Name the gas when acid reacts with metal carbonate.

  4. What is neutralisation?

  5. What is pH of neutral solution?

  6. Name one natural indicator.

  7. Why are antacids used?

  8. Write formula of baking soda.

🔹 2 Marks

  1. What happens when CO₂ is passed through lime water? Write equation.

  2. Explain why acid should be added to water, not water to acid.

  3. Give two properties of acids and bases.

  4. What is pH value of acid rain?

  5. Mention any two uses of washing soda.

🔹 3–4 Marks

  1. Explain with diagram the reaction of zinc granules with dilute sulphuric acid.

  2. What are the products of chloro–alkali process? Write one use of each.

  3. Differentiate between strong acid and weak acid.

  4. Write the molecular formula and two uses of:
    a) Bleaching powder b) Plaster of Paris

  5. Explain the importance of pH in our daily life with examples.

🧠 Quick Recap

Concept Key Idea Example
Acid     Produces H⁺     HCl
Base         Produces OH⁻     NaOH
Neutralisation     Acid + Base → Salt + Water     HCl + NaOH → NaCl + H₂O
pH     Measures acidity     0 – 14 scale
Salt     Product of neutralisation     NaCl

💡 Smart Tips

✅ Remember “A R B B” → Acid = Red, Base = Blue.
✅ pH < 7 → Acidic ; pH > 7 → Basic.
✅ To dilute acid – Add acid to water, never the reverse!
✅ Practice equations daily – small steps give full marks!


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