Best NCERT Solutions for Class 10 Science Chapter 2 Acid, Bases and Salts

NCERT Solutions for Class 10 Science Chapter 2-Acid, Bases and Salts

Best Access NCERT Solutions for Class 10 Science Chapter 2 Acid, Bases and Salts .In the realm of chemistry, salts, acids, and bases are essential for a variety of chemical reactions and practical uses. Comprehending these compounds is crucial not just for learning but also for real-world applications, such cleaning, cooking, and even biological functions.

exercise 1

1. You Have Been Provided With Three Test Tubes. One of Them Contains Distilled Water and the Other Two Contain an Acidic Solution and a Basic Solution, Respectively. If You Are Given Only Red Litmus Paper, How Will You Identify the Contents of Each Test Tube?

Answer: Bases are shown with red litmus paper, which can become blue when a base is present.

Let’s label the three test tubes that are provided as A, B, and C. Place the red litmus paper that comes with each solution. In test tube A, if the red litmus paper becomes blue, it indicates the presence of a base; if not, it indicates the presence of an acid or neutral.

Currently, a drop of test tube A’s solution is placed on the red litmus paper. We perform the same procedure with solutions B and C. One of the three is ruled out as a base if either of them becomes blue. Let’s assume that B is the fundamental example.

Any one of the other two (A and C) solutions can be neutral or acidic. A drop of basic solution is combined with a drop of each of the other two solutions individually, and the nature of the combinations’ drops is examined to determine if they are acidic or neutral. The second solution is neutral (C) if the colour of the red litmus changes to blue, and acidic (A) if the colour does not change. This is due to the fact that basic and acidic solutions cancel each other out. Each test tube’s contents can be identified in this manner.

Exercise 2

1. Why Should Curd and Sour Substances Not Be Kept in Brass and Copper Vessels?

Answer: Lactic acid is found in curd, and other sour foods also include certain acids. Therefore, the acid in curd and other sour things reacts with the metal when they are stored in brass and copper vessels, releasing toxic chemicals and hydrogen gas that contaminate the food.

2. 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?

Answer: Hydrogen gas is liberated when an acid reacts with a metal.

example

Take some pieces of zinc granules in a test tube and add $H_{2} S O_{4}$ to it.
Shake it and pour the resulting gas into a soapy mixture.-There are bubbles in the soapy mixture.-Hydrogen gas is present in these soap bubbles.
-The chemical equation of the reaction is:

$H_{2} S O_{4} + Z n \to Z n S O_{4} + H_{2} ↑$

3. Metal Compound Reacts With Dilute Hydrochloric Acid To Produce Effervescence. The Gas Evolved Extinguishes a Burning Candle. Write a Balanced Chemical Equation for the Reaction if One of the Compounds Formed is Calcium Chloride.

Answer: Water, carbon dioxide, and calcium chloride are the products of the reaction between calcium carbonate, a metal compound, and diluted hydrochloric acid. The carbon dioxide generated has the power to put out a candle that is burning by taking away its oxygen supply.

The balanced chemical equation for the reaction is:

C a C O 3 (s) c a l c i u m c a r b o n a t e + 2 H C l (a q) h y d r o c h l o r i c a c i d \to C a C l 2 (a q) c a l c i u m c h l o r i d e + C O 2 (g) c a r b o n d i o x i d e + H 2 O (l) w a t e r

Best Access NCERT Solutions for Class 10 Science Chapter 2 Acid, Bases and Salts

Exercise 3

1. Why do $HCl, HN O_{3},$ etc., Show Acidic Characters in Aqueous Solutions While Solutions of Compounds Like Alcohol and Glucose Do Not Show Acidic Character?

Answer:

Any substance that is acidic does so because hydronium ions (H3O+) or hydrogen ions (H+) are present in any solution. In a watery mixture, HCl

together with HNO3

separates and produces hydrogen ions. The hydrogen ions mix with water vapour.

to create ions of hydronium.

The hydrogen ions combine with $H_{2} O$ to form hydronium ions. The reaction is as follows:

H C l (a q) \to H + + C l -

H + + H 2 O \to H 3 O +

Due to the presence of hydronium ions $H C l, H N O_{3},$ etc., show acidic characters.

Although hydrogen is present in the aqueous solutions of alcohol and glucose, it is unable to dissociate in water to form hydrogen ions. As a result, they lack an acidic personality.

2. Why Does an Aqueous Solution of an Acid Conduct Electricity?

Answer: In an aqueous solution, acids tend to breakdown into hydrogen ions (H+) or hydronium ions (H3O+). These ions are moving, which allows the solution to conduct electricity. Thus, electricity can be conducted by an acid in aqueous solution.

3. Why Does Dry HCl Gas Not Change the Colour of the Dry Litmus Paper?

Answer:

The existence of hydronium (H3O+) or hydrogen (H+) ions in an aqueous solution is the cause of its acidic nature. Since an acid may only dissociate to produce ions in an aqueous solution, dry HCl gas is devoid of hydrogen or hydronium ions. The hydrogen ions cause the litmus paper to change colour. Therefore, in this instance, the dryness of the HCl gas and the litmus paper will not cause a colour change.

4. While Diluting an Acid, Why is It Recommended That the Acid Should Be Added to Water and Not Water to the Acid?

Answer:

Since the dissolution of an acid in water is an exothermic reaction that emits heat, it is always advised to add acid to the water in order to dilute the acid. When water is put to acid, a lot of heat is produced, which causes the mixture to spill and result in burns and other injuries that could cause accidents.

5. How is the Concentration of Hydronium ions $(H_{3} O^{+})$ Affected When a solution of an acid is Diluted?

Answer: Water is added to an acid solution after it has been diluted. Dilution causes a drop in the hydronium ion concentration (H3O+) per unit volume, which in turn causes the acid’s strength to diminish.

6. How is the Concentration of Hydroxide ions $(O H^{-})$ Affected When Excess Base is Dissolved in a Solution of Sodium Hydroxide?

Answer: Concentration occurs in a solution when too much base is dissolved in it. As a result, the base’s strength would rise together with the concentration of hydroxide ions (OH-) per unit volume.

Exercise 4

1. You Have Two Solutions, A and B. the pH of Solution A is 6 and pH of Solution B is 8. Which Solution Has More Hydrogen Ion Concentration? Which of These is Acidic and Which One is Basic?

Answer:

A solution is said to be basic if its pH is larger than 7 (pH > 7), and acidic if it is less than 7 (pH < 7). As a result, the pH = 6 solution will be acidic and contain a higher concentration of hydrogen ions (H+) than the pH = 8 solution, which will be basic. There is a higher concentration of hydroxide ions (OH−) in the pH = 8 solution.

2. What Effect Does the Concentration of $({H^{+}}_{(aq)})$ Ions Have on the Nature of the Solution?

Answer:

The solution gets more acidic as the concentration of hydrogen ions (H+) rises. Conversely, as the amount of hydrogen ions in the solution decreases, the solution becomes more basic and less acidic.

3. Do Basic Solutions Also Have $({H^{+}}_{(aq)})$ ions? If yes, Then Why are These Basic?

Answer:

yes, (H+(aq)) ions are also present in the basic solution. On the other hand, their concentration is lower than that of hydroxide (OH−) ions, which renders the solution basic.

4. Under What Soil Condition Do You Think a Farmer Would Treat the Soil of His Fields With Quick Lime (Calcium Oxide) or Slaked Lime (Calcium Hydroxide) or Chalk (Calcium Carbonate)?

Answer:

A good basis is thought to be chalk (calcium carbonate), quick lime (calcium oxide), or slaked lime (calcium hydroxide). The farmer would treat the soil with these compounds to improve its basicity if it were acidic, which would make it unsuitable for cultivation.

Exercise 5

1. What is the common name of the compound $CaOC l_{2}$ ?

Answer: Bleaching powder is the popular name for the specified chemical, CaOCl2.

2. Name the Substance Which on Treatment With Chlorine Yields Bleaching Powder?

Answer: Bleaching powder is produced when the chemical calcium hydroxide (Ca(OH)2) is treated with chlorine.

3. Name the Sodium Compound Which is Used for Softening Hard Water.

Answer: Hard water can be softened with sodium compounds such as washing soda (Na2CO3.10H2O).

4. What Will Happen if a Solution of Sodium Hydrocarbonate Is Heated? Give the Equation of the Reaction Involved.

Answer: When sodium hydrocarbonate or sodium hydrogen carbonate solutions are heated, carbon dioxide gas is released along with the formation of sodium carbonate and water.

The Equation is as Follows:

2 N a H C O 3 s o d i u m h y d r o g e n c a r b o n a t e -\to Δ N a 2 C O 3 s o d i u m c a r b o n a t e + H 2 O w a t e r + C O 2 ↑ c a r b o n d i o x i d e

5. Write an Equation to Show the Reaction Between Plaster of Paris and Water.

Answer: One way to depict the chemical equation is as follows:

C a S O 4 . 1 2 H 2 O p l a s t e r o f p a r i s + 1 1 2 H 2 O w a t e r \to C a S O 4 .2 H 2 O g y p s u m

NCERT Exercises

1. A Solution Turns Red Litmus Blue, Its pH Is Likely To Be

a) 1

b) 4

c) 5

d) 10

Answer: (d). Bases become blue-tinged red. pH > 7 is found in basic solution. Given that the solution turns red-litmus blue, pH 10 is most likely the result.

2. 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

Answer: (b). The acid (HCl) in the solution combines with the crushed eggshells to produce carbon dioxide, a gas that turns the lime water frothy. There is calcium carbonate (base) in egg shells.

CaCO3(s)calciumcarbonate+2HCl(aq)hydrochloricacid→CaCl2(aq)calciumchloride+CO2(g)carbondioxide+H2O(l)water

3. 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) 8mL

c) 12 mL

d) 16 mL

Answer: (d) 16 mL

Ten millilitres of a NaOH solution neutralises 8 millilitres of an HCl solution. As a result, 20 millilitres of NaOH solution neutralises

$\frac{10}{8} \times \frac{20}{?}$ mL =16 mL of HCl solution.

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

a) Antibiotic

b) Analgesic

c) Antacid

d) Antiseptic

Answer: (c) An antacid is frequently used to treat dyspepsia.

5. Write Word Equations and Then Balanced Equations for the Reaction Taking Place When−

a) Dilute Sulphuric Acid Reacts with Zinc Granules.

Answer: Word Equation: Sulphuric acid + Zinc → Zinc sulphate + Hydrogen

Balanced Equation: $H_{2} S O_{4 (a q)} + Z n_{(s)} \to Z n S O_{4 (a q)} + H_{2 (g)} ↑$

b) Dilute Hydrochloric Acid Reacts with Magnesium Ribbon.

Answer: Word Equation: Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen

Balanced Equation: $2 H C l + M g_{(s)} \to M g C l_{2 (a q)} + H_{2 (g)} ↑$

c) Dilute Sulphuric Acid Reacts with Aluminium Powder.

Answer: Word Equation: Sulphuric acid + Aluminium → Aluminium sulphate + Hydrogen

Balanced Equation: $3 H_{2} S O_{4 (a q)} + 2 A l_{(s)} \to A l_{2} {(S O_{4})}_{3 (a q)} + 3 H_{2 (g)} ↑$

d) Dilute Hydrochloric Acid Reacts with iron Filings.

Answer: Word Equation: Hydrochloric acid + Iron → Ferric chloride + Hydrogen

Balanced Equation: $6 H C l + 2 F e_{(s)} \to 2 F e C l_{3 (a q)} + 3 H_{2 (g)} ↑$

6. Compounds Such As Alcohols and Glucose Also Contain Hydrogen but Are Not Categorized As Acids. Describe an Activity To Prove It.

Answer:

Action:

A cork that is stored in a 100 mL beaker has two nails attached to it.

b. After that, a switch and a lightbulb are used to link the nails to the terminals of a 6-volt battery.

c. After adding some diluted HCl to the beaker, the current is turned on.

d. Next, the experiment is carried out using solutions of alcohol and glucose.

Notes:

In the HCl solution, the light bulb glows; in the glucose or alcohol solutions, it does not glow.

Result:

In aqueous solution, HCl dissociates into $H^{+}$ and $C l^{-}$ ions. These ions conduct electricity in the solution resulting in the glowing of the bulb. On the other hand, the glucose or alcohol solution does not dissociate into ions. Therefore, the bulb does not glow.

Conclusion:

All acids contain hydrogen but not all compounds containing hydrogen are acids.

So, alcohols and glucose contain hydrogen, but they are not categorised as acids.

7. Why Does Distilled Water Not Conduct Electricity, Whereas Rain Water Does?

Answer: Water that has been distilled is pure and devoid of ionic species. It does not conduct electricity as a result. Rainwater is an impure form of water that conducts electricity because it contains a lot of ionic species, such as acids.

8. Why Do Acids not Show Acidic behaviour in the Absence of Water?

Answer:

The acidic behaviour of acids is caused by their dissociation, which can only occur in an aqueous solution. Because the dissociation of hydrogen ions from an acid only happens in the presence of water, acids do not exhibit acidic behaviour when there is no water present.

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

a) Neutral

Answer: Solution D with pH=7

b) Strongly Alkaline

Answer: Solution C with pH=11

c) Strongly Acidic

Answer: Solution B with pH=1

d) Weakly Acidic

Answer: Solution A with pH=4

e) Weakly Alkaline

Answer: Solution E with pH=9

f) Arrange the pH in Increasing Order of Hydrogen-ion Concentration.

Answer: The pH can be arranged in the increasing order of the concentration of hydrogen ions as:

11 < 9 < 7 < 4 < 1

10. 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 $(C H_{3} COOH)$ is Added to Test Tube B. In Which Test Tube will the Fizzing Occur More vigorously and why?

Answer:

Test tube A experiences a significant fizzing when hydrochloric acid (HCl) is applied. This is due to the fact that HCl produces more hydrogen (H+) ions and is a stronger acid than acetic acid (CH3COOH). Therefore, fizzing happens because HCl creates hydrogen gas more quickly.

11. Fresh Milk Has a pH of 6. How Do You Think the pH Will Change As It Turns Into Curd? Explain Your Answer.

Answer:

Fresh milk has a pH of 6. The pH will drop when it turns into curd because curd contains lactic acid, which lowers pH.

12. 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?

Answer:

Due to the production of lactic acid, milk does not curdle as quickly in an alkaline environment as it does in an acidic one.

b) Why Does This Milk Take a Long Time To Set As Curd?

Answer: The base added to the milk neutralises the acids produced to set the curd since this milk is somewhat more basic than regular milk. As a result, the curd takes longer to set.

13. Plaster of Paris Should Be Stored in a Moisture-Proof Container. Explain Why?

Answer: Because plaster of paris (POP) is a powdery substance that can absorb moisture or water to become gypsum, a hard solid mass, it should be stored in a container that can withstand moisture. The following is how the response happens:

CaSO4.12H2Oplasterofparis+112H2Owater→CaSO4.2H2Ogypsum(hardsolid)

14. What is a Neutralisation Reaction? Give Two Examples.

Answer: Neutralisation Reaction: A neutralisation reaction is a reaction between an acid and a base that results in the formation of salt and water.

For example:

1. $\underset{b a s e}{N a O H} + \underset{a c i d}{H C l} \to \underset{s a l t}{N a C l} + \underset{w a t e r}{H_{2} O}$

2. During indigestion (caused due to the production of excess acid in the stomach), we take an antacid (milk of magnesia, $M g {(O H)}_{2}$ which is basic in nature). The antacid neutralises the excess of acids and thus gives relief from indigestion.