Chapter 2 of the Class 10 Science curriculum focuses on the fascinating world of acids and bases chemical reactions. From the sour taste of lemon to the fizz in baking soda, this chapter explains it all. This chapter is crucial for CBSE board exam preparation, and these revision notes will help you quickly grasp important concepts, chemical reactions, and practical applications.
📌What are Acid, Base and Salt?
🔹Acids
- Acids are substances that have a sour taste and turn blue litmus paper red.
- They release hydrogen ions (H⁺) in aqueous solutions and are ionisable compounds.
- Examples: Hydrochloric acid (HCl), Sulphuric acid (H₂SO₄).
🔹Bases
- Bases taste bitter and turn red litmus paper blue.
- They release hydroxide ions (OH⁻) in solution.
- Examples: Sodium hydroxide (NaOH), Calcium hydroxide (Ca(OH)₂).
🔹Salts
- Salt formation occurs during the reaction between an acid and a base, known as a neutralisation reaction.
📌Acids and Bases Reaction
🔹1. Reaction of Acids with Metals
Acids react with metals to produce hydrogen gas and a corresponding salt.
Example:Zn+H2SO4→ZnSO4+H2↑Zn+H2SO4→ZnSO4+H2↑
🔹2. Reaction of Acids with Metal Carbonates and Metal Bicarbonates
Acids react with metal carbonates and bicarbonates to produce carbon dioxide, water, and a salt.
Example:Na2CO3+2HCl→2NaCl+H2O+CO2↑Na2CO3+2HCl→2NaCl+H2O+CO2↑
🔹3. Reaction of Bases with Metals
Bases like NaOH react with certain metals such as zinc to produce hydrogen gas.
Example:2NaOH+Zn→Na2ZnO2+H2↑2NaOH+Zn→Na2ZnO2+H2↑
🔹4. Reaction of Bases with Non-Metal Oxides
Bases react with non-metal oxides like CO₂ to form salt and water, indicating non-metal oxides are acidic in nature.
Example:Ca(OH)2+CO2→CaCO3+H2OCa(OH)2+CO2→CaCO3+H2O
📌Chemical Properties of Acids and Bases You Must Know
- Acids: Conduct electricity, have a pH less than 7, corrode metals, react with carbonates.
- Bases: Slippery to touch, have a pH more than 7, bitter in taste, neutralise acids.
📌pH Scale and Universal Indicator
- The pH scale measures the hydrogen ion concentration in a solution.
- Values below 7 represent acids, above 7 represent bases.
- A universal indicator is a mixture of dyes that shows different colours at different pH levels.
📌 Practical Applications Acids and Bases
- Baking powder: Used in baking as a leavening agent; releases CO₂ gas.
- Plaster of Paris (Calcium sulphate hemihydrate): Used for setting fractured bones.
- Washing soda (Na₂CO₃·10H₂O): Used in cleaning, softening water.
- Antacids: Substances like magnesium hydroxide neutralize stomach acid.
Important Compounds to Remember
| Compound | Formula | Application |
|---|---|---|
| Sodium Hydroxide | NaOH | Soap making |
| Hydrochloric Acid | HCl | Cleaning steel |
| Sodium Carbonate | Na₂CO₃ | Washing soda |
| Calcium Sulphate | CaSO₄ | Plaster of Paris |
📌 Strong vs Weak Acids and Bases
- Strong acids (e.g., HCl) completely ionize in water.
- Weak acids (e.g., acetic acid) partially ionize.
- Similarly, strong bases (e.g., NaOH) completely dissociate, while weak bases (e.g., ammonium hydroxide) do not.
📌Salt Formation During Acids and Bases Reaction
When an acid reacts with a base, the result is the formation of a salt and water. This process is called a neutralisation reaction because the acid and base neutralize each other’s properties.
General Equation:Acid+Base→Salt+WaterAcid+Base→Salt+Water
Example:HCl+NaOH→NaCl+H2OHCl+NaOH→NaCl+H2O
- Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl), a common salt, and water.
🔚 Key Equations to Remember
- NaOH + HCl → NaCl + H₂O
- HCl + Zn → ZnCl₂ + H₂↑
- Na₂CO₃ + HCl → NaCl + CO₂ + H₂O
- Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
- CaSO₄·½H₂O + H₂O → CaSO₄·2H₂O
This chapter not only forms a core part of the CBSE syllabus but also builds the foundation for higher studies in chemistry. Understanding concepts like acids and bases reaction, neutralisation, and salt formation, alongside applications of baking powder, washing soda, and antacids, ensures better exam readiness and scientific insight.
See more:
Chapter 1:Chemical Reactions and Equations
Chapter 3: Metals and Non-Metals