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NCERT Solutions for Class 10 Science Chapter 2 (2025-2026)

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts brings chemistry alive by connecting it to your everyday experiences - from the sourness of citrus fruits and vinegar to the slippery feel of soap and the fizz of antacids. Understanding acids, bases, and salts is essential not just for exams but for comprehending the chemical world around you, including how your body maintains pH balance and why certain substances neutralize each other. This chapter is part of the comprehensive NCERT Solutions Class 1o Science series, which covers all chapters in detail.

Each solution has been structured with CBSE board examination requirements in focus, helping students tackle everything from indicator-based questions to pH calculations and salt identification. Mastering this chapter lays a solid foundation for understanding electrochemistry, chemical equilibrium, and organic chemistry in senior classes.

NCERT Solutions for Class 10 Science Chapter 2 - All Exercise Questions

Acids, Bases and Salts

Medium

A solution turns red litmus blue, its pH is likely to be

(a) 1
(b) 4
(c) 5
(d) 10

Acids, Bases and Salts

Medium

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky.
The solution contains

(a) NaCl
(b) HCl
(c) LiCl
(d) KCl

Acids, Bases and Salts

Medium

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be

(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL

Acids, Bases and Salts

Medium

Which one of the following types of medicines is used for treating indigestion?

(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic

Acids, Bases and Salts

Medium

Write word equations and then balanced equations for the reaction taking place when –

(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.

Acids, Bases and Salts

Medium

Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.

Acids, Bases and Salts

Easy

Why does distilled water not conduct electricity, whereas rain water does?

Acids, Bases and Salts

Medium

Why do acids not show acidic behaviour in the absence of water?

Acids, Bases and Salts

Medium

Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is:

(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Acids, Bases and Salts

Easy

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?

Acids, Bases and Salts

Easy

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Acids, Bases and Salts

Medium

A milkman adds a very small amount of baking soda to fresh milk.

(a)Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b)Why does this milk take a long time to set as curd?

Acids, Bases and Salts

Medium

Plaster of Paris should be stored in a moisture-proof container. Explain why?

Acids, Bases and Salts

Medium

What is a neutralisation reaction? Give two examples.

Acids, Bases and Salts

Medium

Give two important uses of washing soda and baking soda.

Class 10 Chapter 2 Science Questions & Answers –Acids, Bases and Salts

Q1. A solution turns red litmus blue, its pH is likely to be

(a) 1

(b) 4
(c) 5
(d) 10

Solution: (d) 10

Q2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky.

The solution contains

(a) NaCl
(b) HCl
(c) LiCl
(d) KCl

Solution:

(b) HCl

Q3. 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be

(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL

Solution:

(d) 16 mL

Q4. Which one of the following types of medicines is used for treating indigestion?

(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic

Solution: (c) Antacid

Q5. Write word equations and then balanced equations for the reaction taking place when –

(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.

Solution:

\begin{matrix} (a) Dilute sulphuric acid reacts with zinc granules \\ H_{2} {SO}_{4} + Zn \to {ZnSO}_{4} + H_{2} ↑ \\ (b) Dilute hydrochloric acid reacts with magnesium ribbon \\ 2 HCl + Mg \to {MgCl}_{2} + H_{2} ↑ \\ (c) Dilute sulphuric acid reacts with aluminium powder \\ 3 H_{2} {SO}_{4} + 2 Al \to {Al}_{2} {({SO}_{4})}_{3} + 3 H_{2} ↑ \\ (d) Dilute hydrochloric acid reacts with iron filings \\ 6 HCl + 2 Fe \to 2 {FeCl}_{3} + 3 H_{2} ↑ \end{matrix}

Q6. Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.

Solution:

Acidic and basic solutions in water conduct electricity because they produce hydrogen and hydroxide ions respectively. Compounds such as alcohols and glucose also contain hydrogen but they do not ionise in the solution to give H⁺ ions, hence are not categorized as acids.

To prove this an experiment based activity can be conducted.

Procedure:
Two nails are fitted on a cork and are kept in a 100 mL beaker. Then these are connected to the two terminals of a 6-volt battery through a bulb and a switch. Now, some dilute HCl is poured in the beaker and current is allowed to pass through the circuit. The same experiment is then performed with glucose and alcohol solutions separately in place of HCl.

Observation:
It is observed that the bulb glows in HCl solution only and not in glucose and alcohol.
The reason is that HCl solution dissociates into H⁺ and Cl^– ions which conduct electricity in the HCl solution while glucose and alcohol solutions do not dissociate into ions and so, do not conduct electricity. That is why we find the bulb glowing in HCl solution only.

Conclusion:

The above activity proves that all acids contain hydrogen but not all the compounds which contain hydrogen are acids. Due to this reason compounds such as alcohols and glucose although contain hydrogen, but are not categorised as acids.

Q7. Why does distilled water not conduct electricity, whereas rain water does?

Solution:

Distilled water is the purest form of water without any impurities in it. As distilled water does not contain ions therefore, it does not conduct electricity.

Rain water is an impure form of water contains many ionic species as impurity. These ions are responsible for electrical conductivity of rain water.

Q8. Why do acids not show acidic behaviour in the absence of water?

Solution: The acidic behaviour of a substance is due to the presence of H⁺ ions. As acids do not dissociate to produce H⁺ ions in the absence of water so they do not show acidic behaviour.

Q9. Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is:

(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Solution:

1. Neutral → D (as its pH value is equal to 7)
2. Strongly alkaline → C (as its pH value is 11)
3. Strongly acidic → B (as its pH value is equal to 1)
4. Weakly acidic → A (as its pH value is equal to 4 and more than solution B)
5. Weakly alkaline → E (as its pH value is equal to 9 and less than C)

The pH value in the increasing order of hydrogen ion concentration is:
11< 9 < 7 < 4 < 1

Q10. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?

Solution:

In both the test tubes hydrogen gas is formed. The hydrochloric acid (HCl) is stronger acid than acetic acid (CH₃COOH) so more hydrogen gas is formed in test tube A which results in vigorous fizzing.

Q11. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Solution:

When milk is turned into curd then its pH value will decrease due to the production of lactic acid in curd which is acidic in

Q12. A milkman adds a very small amount of baking soda to fresh milk.

(a)Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b)Why does this milk take a long time to set as curd?

Solution:

1. By adding small amount of baking soda, the milkman shifts the pH of the fresh milk from 6 to slightly alkaline so that in basic form it will not spoil easily and will take a longer time for setting into curd.
2. This milk takes a long time to set as curd because the lactic acid produced in the milk due to bacterial action is neutralised by the baking soda. Hence, this milk takes longer time to set as curd.

Q12. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Solution:

The Plaster of Paris should be stored in a moisture-proof container as it absorbs water from moisture and turn into hard mass called Gypsum as shown in following reaction:

$\underset{Plaster of Paris}{{CaSO}_{4} . \frac{1}{2} H_{2} O} + 1 \frac{1}{2} H_{2} O \to \underset{Gypsum}{{CaSO}_{4} \cdot 2 H_{2} O}$

Q13. What is a neutralisation reaction? Give two examples.

Solution:

The reaction between an acid and a base to give salt and water is known as neutralisation reaction. The effect of a base is nullified by an acid and vice-versa. In general, a neutralisation reaction can be written as:

$\begin{matrix} Base + Acid \to Salt + water \\ NaOH + HCl \to NaCl + H_{2} O \\ {Ca(OH)}_{2} + H_{2} {SO}_{4} \to {CaSO}_{4} + H_{2} O \end{matrix}$

Q14. Give two important uses of washing soda and baking soda.

Solution:

(a) Two important uses of washing soda are:
(i) It is used in the manufacturing of soap and glass.
(ii) It is used to remove the permanent hardness of water.

(b) Two important uses of baking soda are:
(i) It is used for making baking powder.
(ii) It is used in soda- fire extinguishers.

NCERT Solutions for Class 10 Science Chapter 2 – FAQs

Q1. Why do compounds like HCl show acidic behavior in water while glucose and alcohol don't, even though they contain hydrogen?

Original Explanation: The key difference lies in ionization. When HCl dissolves in water, it breaks apart into H⁺ and Cl⁻ ions. These free hydrogen ions (H⁺) are what make a solution acidic.

On the other hand, glucose (C₆H₁₂O₆) and alcohol (C₂H₅OH) also have hydrogen atoms, but these hydrogen atoms are tightly bonded to carbon or oxygen atoms. They don't separate as H⁺ ions when dissolved in water. Without free H⁺ ions, there's no acidic character.

Think of it this way: Having hydrogen doesn't automatically make something acidic—it's about whether that hydrogen can be released as H⁺ ions in solution.

Q2. How would you identify distilled water, an acidic solution, and a basic solution using only red litmus paper?

Original Explanation: Here's a systematic approach:

Step 1: Dip red litmus paper in all three test tubes. The basic solution will turn the red litmus blue. Now you've identified the base.

Step 2: Take the blue litmus paper you just created and test the remaining two solutions. The acidic solution will turn this blue litmus back to red, while distilled water won't change the color.

Step 3: The third solution that showed no color change in both tests is distilled water (neutral).

This works because bases turn red litmus blue, acids turn blue litmus red, and neutral substances don't affect litmus at all.

Q3. What happens in a neutralization reaction? Provide examples.

Original Explanation: Neutralization occurs when an acid reacts with a base, producing two products: salt and water. The H⁺ ions from the acid combine with OH⁻ ions from the base to form H₂O, while the remaining ions form a salt.

Example 1: Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water HCl + NaOH → NaCl + H₂O

Example 2: Sulfuric acid + Potassium hydroxide → Potassium sulfate + Water H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O

The reaction is called "neutralization" because the acidic and basic properties cancel each other out, resulting in a neutral or nearly neutral solution.

Q.1 (a) Sodium hydroxide is prepared by chlor-alkali process.

$2 NaCl (s) + 2 H_{2} O (l) \to {Cl}_{2} (g) + H_{2} (g) + 2 NaOH (aq)$

Why this process is called so?
(b) What happens when Plaster of Paris is wetted with water?

Ans- (a) It is called chlor-alkali process because of the products formed – chlor for chlorine and alkali for sodium hydroxide.
(b) When Plaster of Paris is wetted with water, it changes to gypsum.

$\underset{Plaster of Paris}{{CaSO}_{4} \cdot 1 / 2 H_{2} O} + 3 / 2 H_{2} O \to \underset{Gypsum}{{CaSO}_{4} \cdot 2 H_{2} O}$

Q.2 (a) How does a change in pH causes tooth decay?
(b) What are antacids?

Ans- (a) Tooth decay starts when pH of the mouth is lower than 5.5. Tooth enamel is made up of calcium phosphate and is insoluble in water but is corroded when pH in the mouth is below 5.5.
(b) Antacids are bases that neutralise the excess acid in our stomach to relieve indigestion and heartburn. An example of antacid is magnesium hydroxide.

Q.3 (a) Suppose you have an unknown solution (A).
Name the scale and its range which can we used to find out whether it is acidic or basic or neutral.
(b) Will the pH of orange juice be more than 7 or less than 7?

Ans- (a) pH scale is used to find if the solution is acidic or basic or neutral.
• If the pH is equal to 7, the solution is neutral.
• If the pH is less than 7, the solution is acidic.
• If the pH is more than 7, the solution is basic.
(b) Orange juice is sour in taste, i.e., it is acidic in nature. Therefore, its pH will be less than 7.

Q.4 Represent the following reactions by a balanced chemical equation:
(a) Iron reacts with sulphuric acid.
(b) Sodium carbonate reacts with acetic acid.
(c) Hydrochloric acid reacts with sodium hydroxide.

$\begin{array}{l} Ans-(a) Fe + H_{2} {SO}_{4} \to {FeSO}_{4} + H_{2} \\ {(b) Na}_{2} {CO}_{3} + 2 {CH}_{3} COOH \to 2 {CH}_{3} COONa + H_{2} O + {CO}_{2} \\ (c) HCl + NaOH \to NaCl + H_{2} O \end{array}$

Q.5 (a) Name two edible acids.
(b) Classify aqueous solution of carbon dioxide as acid or base.
(c) Which acid will produce large number of H⁺ ions and why?
(i) aq. solution of acetic acid
(ii) aq. solution of hydrochloric acid

Ans- (a) Acetic acid and citric acid
(b) Aqueous solution of carbon dioxide is acidic (due to the presence of carbonic acid).
(c) Hydrochloric acid is a strong acid and acetic acid is a weak acid. Therefore, hydrochloric acid will produce large number of H⁺ ions.

Q.6 Tooth enamel is one of the hardest substances in our body. How does it damage due to eating cakes and sweets. What should we do to prevent it?

Ans- Tooth enamel is made up of calcium phosphate, Ca(PO₄)₂. It gets corroded when the pH of the mouth becomes lower than 5.5. When we take cakes and sweets, some particles remain in the mouth after eating. Bacteria present in the mouth produce acid by degradation of sugar and food particles remaining in the mouth after eating. This lowers the pH in the mouth and results in tooth decay.

Tooth decay can be prevented by cleaning the mouth after eating sugary food. We can also use toothpastes which are alkaline to neutralise the excess acid and hence prevent the tooth decay.

Q.7 There are two test tubes – test tube (A) containing HCl and test tube (B) containing NaOH. What changes in colour will be observed when red cabbage indicator is added to them?

Ans- In acidic medium the colour of red cabbage indicator turns red. Therefore, when it is added to test tube (A) containing HCl, red colour will be observed. In basic medium the colour of red cabbage indicator turns green. Thus, when it is added to test tube (B) containing NaOH green colour will be observed.

Q.8 (a) Give an example each of a natural indicator and a synthetic indicator.
(b) What change in colour of red litmus paper is observed when it is dipped in a test tube filled with an acid?

Ans-

(a) Natural indicator: Litmus
Synthetic indicator: Phenolphthalein
(b) No change in colour is observed.

Q.9 What is a neutralisation reaction ?

Ans- A reaction between an acid and an alkali which results in the formation of salt and water is called neutralisation reaction.
Example :- NaOH + HCl → NaCl + H₂O

Q.10 What do you mean by universal indicator?

Ans- A natural indicator is a mixture of several indicators having different pH ranges. It shows many colour changes over a wide range of pH. Each colour corresponds to a certain pH value.

Q.11 What is a salt?

Ans- The substance formed other than water by the neutralisation reaction of an acid with a base is called salt.

$NaOH + HCl \to NaCl + H_{2} O$

Q.12 How does acetic acid (vinegar) help in the preservation of food?

Ans- The growth of micro-organisms responsible for food spoilage is prevented or they are rendered inactive by pickling in vinegar or acetic acid.

Q.13 Why should curd and sour substances not be kept in brass and copper vessels?

Ans- Curd and sour substances contain acids which can react with the metal of the vessel to form poisonous metal compounds. These compounds can cause food poisoning and damage our health.

Q.14 You have given three test tubes, one of them contain distilled water and the other two contain an acid solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

Ans- We put the red litmus paper in all the test tubes, turn by turn. The solution which turns red litmus blue will be a basic solution. The blue litmus paper obtained here, is dipped in the remaining two test tubes, one by one.
The solution which turns the blue litmus paper to red will be the acidic solution and the solution which has no effect on any litmus paper will be neutral and hence is distilled water.

Q.15 Why a substance is acidic or basic in nature?

Ans- Acidic nature of a substance is due to the formation of H⁺ (aq) ions or H₃O⁺(aq) ions in aqueous solution and basic nature of a substance is due to the furnishing of OH^– (aq) ions in solution.

Q.16 Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Ans- Hydrogen gas is liberated when an acid reacts with a metal. For example, when zinc metal reacts with dil. HCl, hydrogen gas is evolved and zinc chloride is formed.

Zn (s) + 2HCl(aq) → ZnCl₂ (aq) + H₂ (g)

The presence of hydrogen gas can be tested by bringing a burning candle near the gas. The gas burns with a pop sound.

Q.17 Write a short note on pH scale.

Ans-

pH : The negative logarithm (base 10) of the hydrogen ion concentration in moles per litre is called pH.
pH = – log₁₀ [H⁺]
A scale for measuring hydrogen ion concentration in a solution is known as pH scale. On the pH scale we can measure pH from 0 (very acidic) to 14 (very alkaline). pH indicates the acidic or basic nature of a solution. Higher the hydronium ion concentration, lower is the pH value.
The pH of a neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution. As the PH value increases from 7 to 14, it represents an increase in OH^– concentration that is, increase in the strength of alkali.

Q.18 What is baking soda? How is it produced? Write two uses of it.

Ans- Baking soda is sodium hydrogen carbonate (NaHCO₃). It is produced using sodium chloride.

$\underset{}{NaCl} + \underset{}{H_{2} O} + \underset{}{{CO}_{2}} + \underset{}{{NH}_{3}} \to {NH}_{4} {Cl + NaHCO}_{3}$

Uses of baking soda –

1. For making baking powder which is a mixture of baking soda and tartaric acid.
2. It is used as a mild antiseptic.

Q.19 A compound which is prepared from gypsum has a property of hardening when mixed with water. Identify the compound. Write the chemical equation of its preparation. Mention two uses of the compound.

Ans- The compound is plaster of Paris ( CaSO₄.(1/2) H₂O)
The chemical name of it, is calcium sulphate hemihydrate.

$\underset{Gypsum}{{CaSO}_{4} \cdot 2 H_{2} O} \overset{373K}{\to} \underset{Calcium sulphate hemihydrate}{{CaSO}_{4} . \frac{1}{2} H_{2} O} + 1 \frac{1}{2} H_{2} O$

Uses of plaster of Paris:

1. It is used for plastering the fractured bones in hospitals.
2. It is used for making toys and statues.

Q.20 What will happen if a solution of sodium hydrogen carbonate is heated?

Ans- A solution of sodium hydrogen carbonate on heating gives sodium carbonate and water, and carbon dioxide gas is liberated.

$2 {NaHCO}_{3} \overset{∆}{\to} {Na}_{2} {CO}_{3} + H_{2} O + {CO}_{2} ↑$

Q.21 What is an acid?

Ans- An acid is a substance which dissociates in aqueous solution to give hydrogen ion or hydronium ion.

Q.22 Name the substance which on treatment with chlorine yields bleaching powder.

Ans- Slaked lime [Ca(OH)₂]

$Ca {(OH)}_{2} + {Cl}_{2} \to {CaOCl}_{2} + H_{2} O Slaked lime$

Q.23 What is the common name of the compound with chemical formula CaOCl₂?

Ans- Bleaching powder

Q.24 What is the chemical name of washing soda?

Ans- The chemical name of washing soda is sodium carbonate decahydrate [Na₂CO₃.10H₂O].

Q.25 What is a base?

Ans- A base is a chemical substance which dissociates in aqueous solution to give hydroxyl ions (OH¯).

Q.26 What is an alkali?

Ans- A base which is soluble in water is called an alkali.

Q.27 Define pH.

Ans- pH is defined as the negative logarithm (base10) of the hydrogen ion concentration in moles per litre.
pH = – log10 [H+]

Q.28 What is an indicator?

Ans- An indicator is a ‘dye’ that changes colour when it is put in an acid or a base (alkali).

Q.29 Write an equation to show the reaction between Plaster of Paris and water.

Ans- CaSO4.12H2OPlaster of Paris+32H2O→CaSO4⋅2H2OGypsum

Q.30 Name two mineral acids.

Ans-

(i) Sulphuric acid (H2SO4)
(ii) Nitric acid (HNO3)

Q.31 Name the sodium compound which is used for softening hard water.

Ans- Washing soda [Na2CO3.10H2O]

Q.32 Identify the compound of calcium which is yellowish white powder and is used for disinfecting drinking water. Write its chemical name and formula. How is it manufactured?

Ans- The compound is bleaching powder.
Chemical name : Calcium oxychloride
Formula: CaOCl2
Bleaching powder is manufactured by the action of chlorine on dry slaked lime, Ca(OH)2.

Ca(OH)2Calcium hydroxide (Slaked lime)+Cl2Chlorine → CaOCl2Calcium Oxychloride (Bleaching powder)+H2OWater

Q.33 A metal compound ‘X’ reacts with dilute hydrochloric acid to produce gas (Y). The gas (Y) evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride. Write names of X & Y.

Ans- Metal compound ‘X’ is calcium carbonate because it reacts with dilute hydrochloric acid to give calcium chloride, water and carbon dioxide gas. The carbon dioxide gas evolved extinguishes a burning candle. Hence, ‘Y’ is carbon dioxide.

CaCO3Calcium carbonate + 2HClHydrochloric acid → CaCl2Calcium chloride + CO2Carbondioxide + H2OWater

Q.34 How is concentration of hydroxide ions (OH-) affected when excess of base is dissolved in a solution of sodium hydroxide?

Ans- Concentration of hydroxide ions (OH-) becomes high when excess base is dissolved in a solution of sodium hydroxide.

Q.35 Why does an aqueous solution of an acid conduct electricity?

Ans- When acid is dissolved in water, hydrogen ions (H+) become free to move and hence they can conduct electricity.

Q.36 What are alkalis?

Ans- The bases which are soluble in water are known as alkalis. For example, NaOH, KOH.

Q.37 What are acid and base indicators?

Ans- Acid and base indicators are dyes or mixtures of dyes which are used to indicate the presence of acids and bases. For example, phenolphthalein, methyl orange.

Q.38 What is bleaching powder? How is it prepared? Write chemical equation involved in the preparation of bleaching powder. Write two uses of bleaching powder.

Ans- Bleaching powder is calcium oxychloride ( CaOCl2). It is prepared by passing chlorine gas over dry slaked lime.

Ca(OH)2Calcium Hydroxide Slaked lime + Cl2Chlorine → CaOCl2Calcium oxy chloride Bleaching powder + H2OWater

Uses –

1. Bleaching powder is used for bleaching cotton and linen in the textile industry and for bleaching wood pulp in paper industry.
2. It is used for disinfecting drinking water to make it free of germs.

Q.39 Fresh milk has a pH 6. How do you think the pH will change as it becomes sour?

Ans- pH of the milk will decrease as it becomes sour. Sour milk contains lactic acid. So, the H+ concentration will increase.

Q.40 Why does distilled water not conduct electricity, whereas rainwater does?

Ans- Distilled water is the purest form of water free from all types of impurities while rainwater has impurities mixed into it which allows movement of ions thus results in the conduction of electricity. Hence, distilled water is a poor conductor of electricity whereas rainwater conducts electricity.

Q.41 Name the acid found in
(a) soft drinks
(b) vinegar

Ans-

(a) Soft drinks :- Carbonic acid
(b) Vinegar :- Acetic acid

Q.42 How does an acid taste?

Ans- An acid has a sour taste.

NCERT Solutions for Class 10 Science Chapter 2 (2025-2026)

NCERT Solutions for Class 10 Science Chapter 2 - All Exercise Questions

Class 10 Chapter 2 Science Questions & Answers –Acids, Bases and Salts

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NCERT Solutions for Class 10 Science Chapter 2 – FAQs

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NCERT Solutions for Class 10 Science Chapter 2 (2025-2026)

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NCERT Solutions for Class 10 Science Chapter 2 – FAQs

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