Class 10 Science Chapter 2 Acid Bases and Salt
Class 10 Science Chapter 2 Acid Bases and Salt introduces students to acids, bases and salts, their properties, chemical reactions, indicators, pH scale, neutralisation and important compounds used in everyday life.
Class 10 Science Chapter 2 Acid Bases and Salt – NCERT Solutions
Acids, bases and salts are common substances that we encounter in everyday life. Lemon juice, vinegar, baking soda, soap and many medicines have properties related to acids or bases.
In this chapter, students learn how acids and bases behave, how indicators can be used to identify them, how acids react with metals and carbonates, and how salts are formed.
The chapter also introduces the pH scale, neutralisation, important salts and several useful chemical compounds.
Pay special attention to chemical equations, observations, pH values and the uses of important salts. These ideas are frequently useful when solving examination questions.
Table of Contents
Class 10 Science Chapter 2 Acid Bases and Salt – Textbook Answers
Find the textbook answers arranged separately according to the chapter sections and page numbers. This makes it easier to locate the answer you need without searching through the entire page.
Textbook Answers – Page 18
Question 1: Identifying distilled water, an acidic solution and a basic solution using red litmus paper.
Answer: Use the red litmus paper to identify the basic solution by its colour change. The blue litmus obtained can then be used to identify the acidic solution. The solution that does not change either litmus paper is neutral.
Textbook Answers – Page 22
Use your existing textbook answers for the questions on this page. Keep each question and answer in a separate answer block.
The section covers reactions of acids with metals and metal carbonates, gases produced during these reactions and related chemical equations.
Textbook Answers – Page 25
This section covers acidic behaviour in aqueous solutions, electrical conductivity, dry HCl, dilution of acids and concentration of hydronium and hydroxide ions.
Textbook Answers – Page 28
This section covers pH, hydrogen-ion concentration, basic solutions and treatment of acidic soil.
Textbook Answers – Page 33
This section covers bleaching powder, sodium carbonate, baking soda and plaster of Paris.
Class 10 Science Chapter 2 Chapter-End Exercise Answers
The chapter-end questions cover indicators, chemical reactions, pH, acids and bases, neutralisation, salts and their uses.
Question 1 – Identifying a Basic Solution
A solution that turns red litmus blue is basic. Therefore, among the given pH values, the alkaline option corresponds to the higher pH value.
Question 2 – Reaction with Eggshells
Eggshells contain calcium carbonate. An acid reacting with calcium carbonate releases carbon dioxide, which turns limewater milky.
Question 3 – Neutralisation
For the same solutions, the amount required for neutralisation can be determined using the proportional relationship between the volumes and concentrations involved.
Question 4 – Medicine for Indigestion
Antacids are used to neutralise excess acid in the stomach.
Question 5 – Acids Reacting with Metals
Acids can react with suitable metals to form a salt and release hydrogen gas. Always write the balanced chemical equation when answering these questions.
Class 10 Science Chapter 2 Acid Bases and Salt – MCQs
Practice these multiple-choice questions to revise the important concepts of acids, bases and salts.
MCQ 1 – Reaction of Zinc with Acids
Which acid is expected to react more vigorously with zinc under comparable conditions?
- Acetic acid
- Hydrochloric acid
- Sodium bicarbonate solution
- Water
MCQ 2 – Property of an Acid
Which property is associated with an acid?
- Turns blue litmus red
- Turns red litmus blue
- Always has pH above 7
- Contains no ions in water
MCQ 3 – pH
A solution with pH below 7 is generally acidic.
MCQ 4 – Strong and Weak Acids
Hydrochloric acid is a strong acid, whereas acetic acid is a weak acid in aqueous solution.
Important Concepts in Class 10 Science Chapter 2
Acids
Acids produce hydronium ions in aqueous solution and show characteristic acidic properties.
Bases
Bases produce hydroxide ions in aqueous solution or accept protons depending on the chemical context.
Indicators
Indicators help identify acidic and basic solutions through characteristic colour changes.
Neutralisation
An acid and a base can react to form salt and water.
pH Scale
The pH scale describes the acidic or basic nature of aqueous solutions.
Salts
Salts are ionic compounds that can be formed through different chemical reactions, including acid-base reactions.
Important Chemical Reactions
Acid + Metal
Example:
Zn + 2HCl → ZnCl2 + H2
Acid + Metal Carbonate
Acid + Base
Example:
HCl + NaOH → NaCl + H2O
Metal Oxide + Acid
pH Scale and Its Importance
The pH scale is used to describe the acidic or basic nature of an aqueous solution.
| pH | General nature |
|---|---|
| Less than 7 | Acidic |
| 7 | Neutral |
| Greater than 7 | Basic / alkaline |
Importance of pH in Everyday Life
pH is relevant to biological processes, digestion, soil conditions, and several household and industrial applications.
Important Salts and Their Uses
Baking Soda
Baking soda is sodium hydrogen carbonate, NaHCO3. It has several household and industrial uses.
Washing Soda
Washing soda is sodium carbonate decahydrate, Na2CO3·10H2O. It is used in several industrial and household applications.
Bleaching Powder
Bleaching powder is commonly represented as CaOCl2 and has applications related to bleaching and disinfection.
Plaster of Paris
Plaster of Paris is calcium sulphate hemihydrate and reacts with water to form gypsum.
Important Equations for Quick Revision
HCl + NaOH → NaCl + H2O
CaCO3 + 2HCl → CaCl2 + H2O + CO2
Class 10 Science Chapter 2 – Quick Revision
- Acids show acidic properties in aqueous solution.
- Bases show basic properties in aqueous solution.
- Indicators can help distinguish acidic and basic solutions.
- Acids can react with suitable metals to release hydrogen.
- Acids react with carbonates to produce carbon dioxide.
- pH values below 7 indicate acidic solutions.
- pH 7 represents a neutral solution under standard conditions.
- pH values above 7 indicate basic solutions.
- Neutralisation produces salt and water.
- Baking soda, washing soda, bleaching powder and plaster of Paris are important compounds discussed in the chapter.
Frequently Asked Questions
What is Class 10 Science Chapter 2 about?
The chapter covers acids, bases and salts, their properties, reactions, indicators, pH, neutralisation and important compounds.
What is the pH of a neutral solution?
A neutral aqueous solution has a pH of 7 under standard conditions.
What happens when an acid reacts with a metal?
Many acids react with suitable metals to form a salt and release hydrogen gas.
What is a neutralisation reaction?
A neutralisation reaction is a reaction between an acid and a base that produces salt and water.
What are the important salts in this chapter?
Important compounds include baking soda, washing soda, bleaching powder and plaster of Paris.
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Class 10 Science Chapter 2 Acid Bases and Salt
Clear, structured solutions and revision notes for Acids, Bases and Salts, including textbook questions, pH, reactions, important salts and MCQs.
Class 10 Science Chapter 2 Acid Bases and Salt — Overview
This page brings the chapter material into one clean, student-friendly format. It covers acids and bases, indicators, reactions with metals and carbonates, hydronium and hydroxide ions, pH, neutralisation and important salts.
Answers are presented in concise language so students can revise the concepts and understand the reasoning behind each answer.
Quick Navigation
Class 10 Science Chapter 2 Acid Bases and Salt — Textbook Answers
Identifying acidic, basic and neutral solutions with red litmus
Why acidic foods should not be stored in brass or copper vessels
Gas released when an acid reacts with a metal
Identifying the metal compound from the gas and salt formed
Why HCl and HNO₃ show acidic character in water
Why aqueous acids conduct electricity
Why dry HCl does not affect dry litmus
Why acid is added to water during dilution
Effect of dilution on hydronium-ion concentration
Effect of adding more base
Comparing solutions with pH 6 and pH 8
Effect of hydrogen-ion concentration
Do basic solutions contain H⁺ ions?
When should a farmer add lime to soil?
Common name of CaOCl₂
Substance used to prepare bleaching powder
Sodium compound used to soften hard water
Heating sodium hydrogen carbonate
Reaction of plaster of Paris with water
Chapter-End Exercise Solutions
The solutions below are concise, original explanations based on the supplied source material.
Q1 — pH of a solution that turns red litmus blue
The correct choice is pH 10, because a basic solution has pH greater than 7.
Q2 — Acid reacting with crushed eggshells
The solution is hydrochloric acid. An acid reacts with calcium carbonate in eggshells and releases carbon dioxide, which turns limewater milky.
Q3 — Neutralisation volume calculation
If 10 mL of NaOH requires 8 mL of the same HCl solution, 20 mL requires twice as much HCl.
Q4 — Medicine for indigestion
The appropriate type is an antacid, which neutralises excess stomach acid.
Q5 — Metal–acid reactions
Zinc with dilute sulfuric acid gives zinc sulfate and hydrogen: Zn + H₂SO₄ → ZnSO₄ + H₂. Magnesium with dilute HCl gives MgCl₂ and H₂: Mg + 2HCl → MgCl₂ + H₂. Aluminium with dilute sulfuric acid gives aluminium sulfate and H₂: 2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂. The supplied source gives an iron/HCl equation as FeCl₃; this item should be checked against the intended school-level reaction before publication.
Q6 — Activity showing that glucose and alcohol are not acids
Prepare aqueous samples and connect them in a simple conductivity circuit. Unlike an acid solution, the glucose and alcohol solutions do not provide sufficient ions to make the bulb glow in the expected school experiment.
Q7 — Distilled water versus rainwater conductivity
Distilled water contains very few dissolved ions, so it conducts very poorly. Rainwater picks up dissolved gases and other substances from the atmosphere, giving it ions and allowing some electrical conduction.
Q8 — Why acids need water to show acidic behaviour
Acidic behaviour in this chapter is linked to the formation of H⁺/H₃O⁺ ions in aqueous medium. Without water, the usual aqueous acidic behaviour is not observed.
Q9 — Classifying pH values 4, 1, 11, 7 and 9
Neutral: D (7). Strongly alkaline: C (11). Strongly acidic: B (1). Weakly acidic: A (4). Weakly alkaline: E (9). For increasing hydrogen-ion concentration, arrange pH from highest to lowest: 11 < 9 < 7 < 4 < 1.
Q10 — Magnesium with HCl versus acetic acid
Fizzing is more vigorous with HCl because it is a strong acid and provides a higher hydrogen-ion concentration under comparable conditions. Hydrogen gas is evolved in the reaction.
Q11 — pH change when milk turns into curd
The pH decreases because lactic acid is formed during curd formation, making the product more acidic.
Q12 — Adding baking soda to fresh milk
A small amount of baking soda makes the milk slightly alkaline. The lactic acid produced during souring must first neutralise the added alkali, so curd formation takes longer.
Q13 — Storage of plaster of Paris
Plaster of Paris should be protected from moisture because water causes hydration and premature setting, reducing its usefulness.
Q14 — Neutralisation reaction
A neutralisation reaction occurs when an acid reacts with a base to form salt and water. Example: HCl + NaOH → NaCl + H₂O.
Q15 — Uses of washing soda and baking soda
Washing soda is used in several industries and for softening hard water. Baking soda is used as an antacid and in baking preparations.
Class 10 Science Chapter 2 Acid Bases and Salt — MCQs
The uploaded source contains MCQs 1–10 and 12; MCQ 11 is not present in the supplied material, so it has not been invented here.
Q1 — Vigorous reaction of zinc with the listed substances
Answer: HCl
Hydrochloric acid is a strong acid and reacts readily with zinc, producing hydrogen.
Q2 — Property identifying an acid
Answer: All of the above
The listed observations are treated as characteristic acid properties in the supplied source.
Q3 — Sample that turns pH paper blue
Answer: Sodium bicarbonate solution
Sodium bicarbonate solution is basic.
Q4 — Solutions with pH 4 and 10
Answer: X is acidic; Y is basic
pH below 7 is acidic and pH above 7 is basic.
Q5 — Article not needed for the pH experiment
Answer: Petri dish
The listed pH experiment requires items such as pH paper and a dropper rather than a petri dish.
Q6 — Test for hydrogen evolved from zinc and NaOH
Answer: Burning splint / matchstick
Hydrogen can be identified by its characteristic pop test.
Q7 — Effect of adding NaCl to a solution of pH 5
Answer: No change in pH
This is the answer given in the supplied source for the stated school-level question.
Q8 — Salt solution with pH 7
Answer: KCl
Among the given options, KCl is the neutral salt identified by the source.
Q9 — Set-up in which no gas is evolved
Answer: IV
The supplied source identifies set-up IV because sodium hydroxide does not react with sodium carbonate in the stated arrangement.
Q10 — Most appropriate set-up for identifying hydrogen from zinc + dilute HCl
Answer: IV
The supplied source identifies set-up IV as the appropriate arrangement.
Q12 — Substance that changes yellowish-orange soil-test pH paper toward greenish blue
Answer: An antacid
The supplied source identifies an antacid as the weakly basic option.
Quick Revision — Acids, Bases and Salts
Acids
- Show acidic character in aqueous solution.
- Increase H⁺/H₃O⁺ concentration in water.
- React with suitable metals to release hydrogen.
- React with carbonates to release carbon dioxide.
Bases
- Have greater OH⁻ concentration in basic aqueous solutions.
- Basic solutions have pH above 7.
- React with acids in neutralisation reactions.
pH
| pH | Nature |
|---|---|
| < 7 | Acidic |
| 7 | Neutral |
| > 7 | Basic |
Important compounds
- CaOCl₂ — bleaching powder
- Ca(OH)₂ — slaked lime
- Na₂CO₃ — washing soda
- NaHCO₃ — sodium hydrogen carbonate / baking soda
- Plaster of Paris — calcium sulfate hemihydrate
Frequently Asked Questions
What is the main focus of Class 10 Science Chapter 2 Acid Bases and Salt?
The chapter focuses on acids, bases and salts, their reactions and properties, indicators, pH, neutralisation and important salts.
What is the pH of a neutral solution?
At the school-level pH scale used in this chapter, a neutral solution has pH 7.
What happens to hydronium-ion concentration when an acid is diluted?
The concentration of H₃O⁺ ions per unit volume decreases.
Why is acid added to water rather than water to acid?
Dilution releases heat. Adding acid slowly to water helps distribute the heat more safely and reduces the risk of sudden splashing.
What is the common name of CaOCl₂?
Bleaching powder.
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