NCERT Solutions for Class 10 Science Chapter 2: Acids, Bases and Salts
Acids, Bases and Salts is one of the highest-scoring chapters in CBSE Class 10 Science, and students who master it often find Chemistry much more approachable throughout their academic journey. This chapter explores how acids and bases behave in aqueous solutions, how they neutralise each other, and how salts are formed as a result of these reactions. At Myclass24, our NCERT Solutions for Class 10 Science Chapter 2 cover every concept with clarity — from the pH scale and indicators to the preparation and properties of important salts like sodium hydroxide, washing soda, baking soda, bleaching powder, and plaster of Paris. Students in India often find the industrial preparation sections tricky, which is why our solutions break down the Chlor-Alkali process and other reactions in a way that is easy to visualise and remember.
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Chapter 2 Deep Dive: Acids, Bases and Salts — Concepts & Tables
Acids, Bases and Salts is a chapter where understanding the logic behind each reaction matters more than rote memorisation. Here is a structured breakdown of all major topics with mobile-friendly tables to make revision quicker and more effective.
Properties of Acids vs Bases
| Property | Acids | Bases |
|---|---|---|
| Taste | Sour | Bitter |
| Feel | Corrosive | Soapy / slippery |
| pH Range | Less than 7 | Greater than 7 |
| Litmus Paper | Turns blue litmus red | Turns red litmus blue |
| H⁺ / OH⁻ ions | Release H⁺ ions in water | Release OH⁻ ions in water |
| Examples | HCl, H₂SO₄, CH₃COOH | NaOH, Ca(OH)₂, NH₄OH |
pH Scale and Its Significance
The pH scale ranges from 0 to 14. A pH of 7 is neutral (pure water). Values below 7 indicate acidic nature, while values above 7 indicate basic nature. Strong acids like HCl have a pH near 0, and strong bases like NaOH have pH near 14. Human blood maintains a pH between 7.35 and 7.45 — a slight deviation causes serious health issues.
Common Indicators and Their Colour Changes
| Indicator | In Acid | In Base | In Neutral |
|---|---|---|---|
| Litmus | Red | Blue | Purple |
| Phenolphthalein | Colourless | Pink | Colourless |
| Methyl Orange | Red / Pink | Yellow | Orange |
| Turmeric | Yellow | Red/Brown | Yellow |
| China Rose | Magenta | Green | Magenta |
Important Salts and Their Uses
| Salt Name | Chemical Formula | Common Use |
|---|---|---|
| Common Salt | NaCl | Food, preservation, Chlor-Alkali process |
| Washing Soda | Na₂CO₃·10H₂O | Cleaning agent, glass & soap industry |
| Baking Soda | NaHCO₃ | Baking, antacid, fire extinguishers |
| Bleaching Powder | Ca(OCl)Cl | Disinfecting water, bleaching cloth/paper |
| Plaster of Paris | CaSO₄·½H₂O | Surgical plasters, chalk, statues |
Neutralisation Reaction
When an acid and a base react together, they produce salt and water. This reaction is called neutralisation. For example: HCl + NaOH → NaCl + H₂O. The heat released during this reaction is called heat of neutralisation. Neutralisation has practical applications in treating soil acidity (using lime), relieving acidity in the stomach (using antacids), and treating wastewater before releasing it into rivers.
CBSE Board: Marks Distribution for Chapter 2
| Topic | Expected Marks | Exam Format |
|---|---|---|
| pH and indicators | 2–3 marks | MCQ + short answer |
| Properties of acids & bases | 3 marks | Short answer |
| Salts and their uses | 3–5 marks | Long answer / table |
| Chlor-Alkali process | 3 marks | Diagram + explanation |
| Neutralisation reactions | 2 marks | Equation-based |
FAQs for NCERT Solutions for Class 10 Science Chapter 2 Acids Bases Salts
Acids are substances that release hydrogen ions (H⁺) when dissolved in water and have a pH below 7. Bases are substances that release hydroxide ions (OH⁻) and have a pH above 7. Acids like hydrochloric acid taste sour, turn blue litmus red, and react with metals to release hydrogen gas. Bases like sodium hydroxide taste bitter, feel slippery, and turn red litmus blue. The key distinction lies in their ion release and effect on indicators. Strong acids like H₂SO₄ fully dissociate while weak acids like acetic acid partially dissociate. Similarly, strong bases like NaOH fully ionise while weak bases like ammonia solution only partially ionise in water.
The pH scale measures the concentration of hydrogen ions in a solution and ranges from 0 to 14. A pH below 7 is acidic, exactly 7 is neutral, and above 7 is basic or alkaline. This scale is extremely important in daily life. Our stomach maintains a pH of around 1.5 to 2 for digestion using hydrochloric acid. When excess acid is produced, we experience acidity — antacids with a higher pH help neutralise it. Soil pH affects crop growth; farmers add lime to acidic soil. Tooth decay occurs when bacteria lower mouth pH below 5.5. Even swimming pools require controlled pH for safety. Understanding pH helps us manage health, agriculture, and industrial processes.
When an acid and a base react with each other, they neutralise each other and form salt and water. This reaction is called a neutralisation reaction. The general equation is: Acid + Base → Salt + Water. For example, hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water: HCl + NaOH → NaCl + H₂O. The heat released in this process is called heat of neutralisation. This reaction has practical applications — antacids neutralise excess stomach acid, bee stings (acidic) are treated with baking soda, and wasp stings (basic) are treated with vinegar. The products formed are always ionic compounds known as salts, which may have various uses.
Sodium hydroxide (NaOH), commonly called caustic soda, is used in making soaps, paper, and as a cleaning agent in drains. It is produced through the chlor-alkali process. Baking soda (NaHCO₃ or sodium hydrogen carbonate) is used in cooking as a leavening agent because it releases carbon dioxide gas when heated, making food fluffy. It is also used in antacids and fire extinguishers. Washing soda (Na₂CO₃·10H₂O or sodium carbonate decahydrate) is used in glass and soap manufacturing and as a cleaning agent to remove grease. It also softens hard water. These compounds are all products derived from common salt (NaCl) and have widespread household and industrial applications.
Strong acids are those that completely dissociate into ions when dissolved in water, releasing all their hydrogen ions. Examples include hydrochloric acid (HCl), sulphuric acid (H₂SO₄), and nitric acid (HNO₃). Weak acids only partially dissociate, releasing fewer hydrogen ions. Examples include acetic acid (vinegar), carbonic acid, and citric acid found in fruits. In Chapter 2, students learn that the strength of an acid depends on its degree of ionisation, not on concentration. A dilute strong acid is still a strong acid. Similarly, concentrated weak acid remains weak. Strong acids have a very low pH, while weak acids have a comparatively higher pH. The concentration affects how much acid is present, not how completely it ionises.