CBSE Class 10 Science Chapter 2 u2014 Acids, Bases and Salts is one of the most important chapters for board exams, carrying 5u20137 marks directly in Class 10 Science. This chapter also forms the foundation for Class 12 Chemistry. These complete NCERT solutions and notes will help you understand all concepts and score full marks.
Chapter Snapshot u2014 CBSE Class 10
| Parameter | Details |
|---|---|
| Chapter | 2 u2014 Acids, Bases and Salts |
| Subject | Science (Class 10) |
| Board Marks | 5u20137 marks (direct questions) |
| Key Topics | Properties of acids/bases, pH, salts, neutralisation |
Acids u2014 Definition and Properties
Arrhenius definition: Acids are substances that produce Hu207a (hydrogen ions) in aqueous solution.
Key properties of acids:
- Sour taste (like lemon juice, vinegar)
- Turn blue litmus red
- pH < 7
- React with metals to produce Hu2082 gas: Acid + Metal u2192 Salt + Hu2082
- React with carbonates to produce COu2082: Acid + Carbonate u2192 Salt + COu2082 + Hu2082O
- React with bases (neutralisation): Acid + Base u2192 Salt + Water
- Conduct electricity in solution (electrolytes)
Common Acids and Their Sources
| Acid | Formula | Natural Source |
|---|---|---|
| Hydrochloric acid | HCl | Gastric juice (stomach) |
| Sulphuric acid | Hu2082SOu2084 | Acid rain |
| Nitric acid | HNOu2083 | Acid rain |
| Citric acid | Cu2086Hu2088Ou2087 | Lemon, orange |
| Acetic acid | CHu2083COOH | Vinegar |
| Tartaric acid | u2014 | Tamarind |
| Oxalic acid | u2014 | Tomato |
| Formic acid | u2014 | Ant sting |
Bases u2014 Definition and Properties
Arrhenius definition: Bases produce OHu207b (hydroxide ions) in aqueous solution.
Alkalis = water-soluble bases (NaOH, KOH, Ca(OH)u2082)
Key properties of bases:
- Bitter taste and soapy feel
- Turn red litmus blue
- pH > 7
- React with non-metallic oxides to form salts
- React with acids (neutralisation)
pH Scale u2014 CBSE Favourite Topic
| pH Range | Nature | Examples |
|---|---|---|
| 0u20136 | Acidic | HCl (pHu22481), Stomach acid (pHu22482), Lemon (pHu22482.5), Vinegar (pHu22483) |
| 7 | Neutral | Pure water, Normal saline |
| 8u201314 | Basic/Alkaline | Blood (pHu22487.4), Seawater (pHu22488), Baking soda (pHu22489), NaOH (pHu224814) |
Important for boards: pH of blood is 7.35u20137.45. pH in stomach = 1.5u20132 (HCl helps digestion). Tooth enamel dissolves at pH < 5.5 (why brushing teeth matters).
Important Salts and Their Uses
| Salt | Chemical Name | Formula | Uses |
|---|---|---|---|
| Common salt | Sodium chloride | NaCl | Food preservation, chlorine production |
| Baking soda | Sodium bicarbonate | NaHCOu2083 | Baking, antacid, fire extinguisher |
| Washing soda | Sodium carbonate decahydrate | Nau2082COu2083.10Hu2082O | Cleaning, glass making, softening hard water |
| Bleaching powder | Calcium hypochlorite | CaOClu2082 | Disinfection, bleaching fabric |
| Plaster of Paris | Calcium sulphate hemihydrate | CaSOu2084.u00bdHu2082O | Plaster casts, sculptures |
NCERT Exercise Solutions u2014 Chapter 2
Q1: A solution turns red litmus blue. Its pH is likely to be:
Answer: The solution is basic (pH > 7). Red litmus turns blue in basic solutions. Likely pH: 8, 9, 10, or higher.
Q2: Plaster of Paris should be stored in a moisture-proof container. Explain why.
Answer: Plaster of Paris (CaSOu2084.u00bdHu2082O) reacts with moisture/water to form gypsum (CaSOu2084.2Hu2082O) and hardens. If stored in a non-moisture-proof container, it will absorb atmospheric moisture, harden, and become useless. Hence moisture-proof storage is essential.
Q3: What is the effect of mixing acid and base (neutralisation)?
Answer: When an acid and a base are mixed, they undergo neutralisation. The Hu207a ions from the acid combine with OHu207b ions from the base to form water. The remaining ions form a salt. The reaction is: Acid + Base u2192 Salt + Water (Hu207a + OHu207b u2192 Hu2082O)
Practice Quiz u2014 Acids, Bases and Salts Class 10
Quiz data missing.
FAQ
What is the difference between acid and base according to Arrhenius theory?
According to Arrhenius theory, an acid is a substance that produces Hu207a ions in aqueous solution (e.g., HCl u2192 Hu207a + Clu207b), while a base produces OHu207b ions in aqueous solution (e.g., NaOH u2192 Nau207a + OHu207b). The neutralisation reaction between an acid and base produces water and a salt.
What is the formula of Plaster of Paris?
Plaster of Paris is calcium sulphate hemihydrate: CaSOu2084.u00bdHu2082O. It is prepared by heating gypsum (CaSOu2084.2Hu2082O) at 373 K. When mixed with water, it rehydrates and sets hard u2014 making it useful for surgical casts, dental impressions, and sculptures. Do not confuse with gypsum (CaSOu2084.2Hu2082O).
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