Important Questions for CBSE Class 10 Science Chapter 2 - Acids, Bases and Salts 2024-25

1 Mark Questions

1. An acid can react with

1.  $\text{AgCl}$

2.  $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$

3.  $PbS{{O}_{4}}$

4.  $\text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}$

Ans: The correct answer is (b) $N{{a}_{2}}C{{O}_{3}}$

2. Which of the following gives $\text{C}{{\text{O}}_{\text{2}}}$ on heating?

1. Slaked

2. Quick lime

3. Limestone

4. Soda ash.

Ans: The correct answer is (c) Limestone

3. Plaster of Paris is made from

1. Limestone

2. Slaked Lime

3. Quick lime

4. Gypsum 

Ans: The correct answer is (d) Gypsum

4. Which is a base and not alkali? 

1.  $\text{NaOH}$

2.  $\text{KOH}$

3. $\text{Fe}{{\left( \text{OH} \right)}_{\text{3}}}$

4.  None

Ans: The correct answer is (c) $\text{Fe}{{\left( \text{OH} \right)}_{\text{3}}}$

5. Chemical formula of baking soda is

1.  $\text{MgS}{{\text{O}}_{\text{4}}}$

2.  $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$

3.  $\text{NaHC}{{\text{O}}_{\text{3}}}$

4.  $\text{MgC}{{\text{O}}_{\text{3}}}$

Ans: The correct answer is (c) $\text{NaHC}{{\text{O}}_{\text{3}}}$

6. The H+ ion concentration of a solution is $\text{1}\text{.0 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{-5}}}\,\text{m}$. The solution is

1. Acidic

2. Alkaline

3. Neutral

  (d) Amphoteric 

Ans: The correct answer is (a) Acidic

7. An aqueous solution with pH-zero is

1. Acidic

2. Alkaline

3. Neutral

  (d) Amphoteric

 Ans: The correct answer is (a) Acidic

8. The setting of Plaster of Paris takes place due to

1. Oxidation

2. Reduction

3. Dehydration

4. Hydration 

Ans: The correct answer is (d) Hydration

  9. The difference of water molecules is gypsum and Plaster of Paris is 

1.  $\dfrac{5}{2}$

2.  $2$

3.  $\dfrac{1}{2}$

4.  $\dfrac{3}{2}$

Ans: The correct answer is (d) $\dfrac{3}{2}$

10. The odor of acetic acid resembles that of

1. Rose

2. Burning Plastic

3. Vinegar

4. Kerosene 

Ans: The correct answer is (c) Vinegar

  11. Washing soda has the formula 

1.  $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.7}{{\text{H}}_{\text{2}}}\text{O}$

2.  $\mathsf{N}{{\mathsf{a}}_{\mathsf{2}}}\mathsf{C}{{\mathsf{O}}_{\mathsf{3}}}\mathsf{.10}{{\mathsf{H}}_{\mathsf{2}}}\mathsf{O}$

3. $\mathsf{N}{{\mathsf{a}}_{\mathsf{2}}}\mathsf{C}{{\mathsf{O}}_{\mathsf{3}}}\mathsf{.}{{\mathsf{H}}_{\mathsf{2}}}\mathsf{O}$

4. $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$

Ans: The correct answer is (b) $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.10}{{\text{H}}_{\text{2}}}\text{O}$

12. Plaster of Paris hardens by

1. Giving off $\text{C}{{\text{O}}_{\text{2}}}$

2. Changing into $\text{CaC}{{\text{O}}_{\text{3}}}$

3. Combining with water

4. Giving out water

Ans: The correct answer is (c) Combining with water

13. Which of the following is evolved when $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$ is heated?

1.  $\text{C}{{\text{O}}_{\text{2}}}$

2.  $\text{CO}$

3. ${{\text{O}}_{\text{2}}}$

4.  No 

Ans: The correct answer is (a) $\text{C}{{\text{O}}_{\text{2}}}$

14. A drop of the liquid sample was put on the pH paper, the paper turned blue. The  liquid sample must be of

1. Lemon Juice

2. HCl

3. Sodium bicarbonate

4. Ethanoic acid

Ans: The correct answer is (c) Sodium bicarbonate

   15. If the pH of the solution is 13, it means that it is

1. Weakly acidic

2. Weakly basic

3. Strongly acidic

4. Strongly Basic

Ans: The correct answer is (d) Strongly Basic

16. How is the concentration of hydronium ions $\left( {{\text{H}}_{\text{3}}}{{\text{O}}^{\text{+}}} \right)$ affected when a solution of acid is diluted?

Ans: If an acid solution is diluted, the hydronium ion concentration decreases.

17. What effect does the concentration of ${{\text{H}}^{\text{+}}}$ ions have on the nature of the solution?

Ans: A higher concentration of ${{\mathsf{H}}^{\mathsf{+}}}$ ions turns the solution acidic in nature.

18. What is the common name of the compound $CaOC{{l}_{2}}$?

Ans: The common name of the compound is Bleaching powder.

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

Ans: Slaked lime (calcium hydroxide) yields bleaching powder in treatment with chlorine.

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

Ans: The compound which is used for softening hard water is Sodium carbonate.

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

1.  $1$

2.  $2$

3.  $5$

4.  $10$

Ans: The correct answer is (d) $10$

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

1.  $NaCl$

2.  $HCl$

3.  $LiCl$

4.  $KCl$

Ans: The correct answer is (b) $\text{HCl}$

23. $10mL$ of a solution of $NaOH$ is found to be completely neutralized by $8mL$ of a given solution of $HCl$. If we take $20mL$ of same solution of $NaOH$, the amount of $HCl$ solution required to neutralize it will be

1.  $4mL$

2.  $8mL$

3.  $12mL$

4.  $16mL$ 

Ans: The correct answer is (d) $\text{16mL}$

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

1. Antibiotics

2. Analgesic

3. Antacid

4. Antiseptic 

Ans: The correct answer is (c) Antacid

25. 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:

1. neutral?

Ans: D

2. strongly alkaline?

  Ans: C

3. strongly acidic?

  Ans: B

4. weakly acidic?

  Ans: A

5. weakly alkaline? 

Ans: E

26. ‘A’ is a soluble acidic oxide and ‘B’ is a soluble base. Compared to pH of pure water.    What will be the pH of (a) solution of A (b) solution of B?

Ans: Since ‘A’ is acidic, the pH will be less than $7$. On the other hand, since ‘B’ is basic, pH will be more than $7$.

2 Marks Questions

1. What happens to the crystals of washing soda when exposed to air?

Ans: Upon exposure of washing soda crystals to air, the following reaction takes place: 

$\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.10}{{\text{H}}_{\text{2}}}\text{O}\xrightarrow{\text{air}}\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.}{{\text{H}}_{\text{2}}}\text{O}\,\,\text{+}\,\,\text{9}{{\text{H}}_{\text{2}}}\text{O}$

In the reaction, the white crystals of washing soda turn into washing powder (white powder).  Efflorescence occurs in the washing soda.

2. What is the chemical name of washing soda? Name three raw materials used in making washing soda by Solvay process?

Ans: The chemical name of washing soda $\left( \text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.10}{{\text{H}}_{\text{2}}}\text{O} \right)$ is sodium carbonate decahydrate.

Ammonia, Brine, and Limestone are used to make washing soda by the Solvay process. 

3. What is efflorescence? Give an example?

Ans:  Upon exposure to air, the loss of the molecules of water of crystallization from a substance is defined as efflorescence. For example, in the reaction given below, the crystals of washing soda turn into washing powder when exposed to air.

$\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.10}{{\text{H}}_{\text{2}}}\text{O}\xrightarrow{\text{air}}\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{.}{{\text{H}}_{\text{2}}}\text{O}\,\,\text{+}\,\,\text{9}{{\text{H}}_{\text{2}}}\text{O}$

4. Why is sodium hydrogen carbonate an essential ingredient in antacids?

Ans: Sodium hydrogen carbonate $\left( \text{NaHC}{{\text{O}}_{\text{3}}} \right)$ is an essential ingredient in antacids because of the basic nature of the salt. It neutralizes the $HCl$ acid released in the stomach. The following reaction takes place,

$\text{NaHC}{{\text{O}}_{\text{3}}}\,\,\text{+}\,\,\text{HCl}\to \text{NaCl}\,\,\text{+}\,\,{{\text{H}}_{\text{2}}}\text{O}\,\,\text{+}\,\,\text{C}{{\text{O}}_{\text{2}}}$

5. Give the name and formula of two

1. strong monobasic acids

Ans: The required answer is:

Hydrochloric acid $\left( \text{HCl} \right)$, Nitric acid $\left( \text{HN}{{\text{O}}_{\text{3}}} \right)$

2. two weak dibasic acids

Ans: The required answer is:

Carbonic acid $\left( {{\text{H}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}} \right)$, oxalic acid $\left( {{\text{C}}_{\text{2}}}{{\text{H}}_{\text{2}}}{{\text{O}}_{\text{4}}} \right)$

6. Why alkalis like sodium hydroxide and potassium hydroxide should not be left exposed to air?

Ans: Alkalis are hygroscopic in nature. Upon exposure to air, they absorb moisture from the surrounding atmosphere and get dissolved in it.

7. Dry ammonia has no action on litmus paper but a solution of ammonia in water turns red litmus paper blue. Why is it so?

Ans: Dry ammonia has no action on the litmus paper because it contains no hydroxyl ions in the absence of water. On dissolving in water, it forms ammonium hydroxide $\left( \text{N}{{\text{H}}_{\text{4}}}\text{OH} \right)$, which is basic in nature because it dissociates to give $\text{N}{{\text{H}}_{\text{4}}}^{\text{+}}$ and $\text{O}{{\text{H}}^{\text{-}}}$ ions. Thus, red litmus paper turns blue.

$\text{N}{{\text{H}}_{\text{3}}}\left( \text{g} \right)\,\,\text{+}\,{{\text{H}}_{\text{2}}}\text{O}\to\text{N}{{\text{H}}_{\text{4}}}\text{OH}\left( \text{aq} \right) $  

$\text{N}{{\text{H}}_{\text{4}}}\text{OH}\left( \text{aq} \right)\to \text{N}{{\text{H}}_{\text{4}}}^{\text{+}}\left( \text{aq} \right)\,\,\text{+}\,\,\text{O}{{\text{H}}^{\text{-}}}\left( \text{aq} \right)$

8. Bleaching powder forms a milky solution in water. Explain.

Ans: Bleaching powder reacts with water to form $\text{Ca}{{\left( \text{OH} \right)}_{\text{2}}}$, which has a milky appearance. The reaction is given by,

$\text{CaOC}{{\text{l}}_{\text{2}}}\text{  +}\,\,{{\text{H}}_{\text{2}}}\text{O}\to \text{Ca}{{\left( \text{OH} \right)}_{\text{2}}}\,\,\text{+}\,\,\text{2HCl}$

9. Why does not an acid show any acidic behavior in the absence of water?

Ans: Water is an ionizing compound. In its presence, acids form an aqueous solution and get ionized. This results in the release of ${{\text{H}}^{\text{+}}}$ions and hence, acidic behavior is shown.

10. Fresh milk has a pH of $6$. What will be the pH value if milk changes into a curd? Justify.

Ans: Lactose is converted to lactic acid when milk changes into a curd. Because of the greater acidic nature, the pH value decreases.

11. What is the reaction between hydrogen in concentration ion concentration of an aqueous solution and pH?

Ans: The reaction is given as

$\text{pH=-log}\left[ {{\text{H}}^{\text{+}}} \right]$, where ${{\text{H}}^{\text{+}}}$ is hydrogen in concentration

12. How will you show that acetic acid is monobasic acid?

Ans: When acetic acid reacts with a basic solution, only one ${{\text{H}}^{\text{+}}}$ ion is replaced by the base, which shows acetic acid is a monobasic acid. For example,

$\text{C}{{\text{H}}_{\text{3}}}\text{COOH}\,\,\text{+ NaOH}\to \text{C}{{\text{H}}_{\text{3}}}\text{COONa}\,\,\text{+}\,\,{{\text{H}}_{\text{2}}}\text{O}$

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

Ans: Brass is an alloy of copper and zinc metals. These metals react with acids present in curd and sour substances to form poisonous soluble salts. Hence, storing curd and sour substances in brass or copper vessels makes them unfit for consumption.

14. 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:  When an acid reacts with a metal, hydrogen gas is liberated. For example,

$\text{Zn + C}{{\text{l}}_{\text{2}}}\to \text{ZnC}{{\text{l}}_{\text{2}}}\text{ + }{{\text{H}}_{\text{2}}}$

We bring a burning splinter near the liberated gas. If the gas is hydrogen, it burns with a pop sound. 

15. Why does an aqueous solution of acid conduct electricity?

Ans: Water is a polarizing compound. Acid gets ionized in an aqueous solution and $H^+$ ions are released. These ions conduct electricity.

16. Why does dry HCl gas not change the color of the dry litmus paper?

Ans:  When litmus paper comes in contact with ${{\text{H}}^{\text{+}}}$ ions, the color of the paper changes. These ions are produced only upon dissolution of $\text{HCl}$ gas in water. Therefore, dry $\text{HCl}$ does not change the color of dry litmus paper.

17. While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Ans: The addition of water to acid leads to a highly exothermic reaction. The intensity of the heat produced can break the glass container or cause severe burns to the person adding it. On the other hand, adding acid to water with constant stirring aids the absorption of the heat produced by water, and any harm/damage is avoided.

18. How is the concentration of hydroxide ions $\left( O{{H}^{-}} \right)$ affected when excess base is dissolved in a solution of sodium hydroxide?

Ans: The dissolution of excess base in a solution of sodium hydroxide will release more hydroxide  $\left( \text{O}{{\text{H}}^{\text{-}}} \right)$ ions. Therefore, it will lead to an increase in the concentration of hydroxide ions. 

19. Do basic solutions also have ${{H}^{+}}$ ions? If yes, then why are these basic?

Ans: The ${{\text{H}}^{\text{+}}}$ ions are present in both acidic and basic solutions. A solution is acidic if the concentration of ${{\text{H}}^{\text{+}}}$ ions is more than $\text{O}{{\text{H}}^{\text{-}}}$ ions. On the other hand, a solution is basic if the concentration of $\text{O}{{\text{H}}^{\text{-}}}$ ions concentration is more than the ${{\text{H}}^{\text{+}}}$ ions.

20. Do basic solutions also have ${{\text{H}}^{\text{+}}}$  ions? If yes, then why are these basic?

Ans: Acidic and basic solutions both have ${{\text{H}}^{\text{+}}}$  ions. The difference is that in acids ${{\text{H}}^{\text{+}}}$  ions concentration is more than $\text{O}{{\text{H}}^{\text{-}}}$ ions concentration while in basic solution $\text{O}{{\text{H}}^{\text{-}}}$ ions concentration is more than ${{\text{H}}^{\text{+}}}$  ions concentration.

21. 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 ions concentration? Which is acidic and which one is basic?

Ans: On a pH scale, any solution having pH value less than $7$ is considered acidic and that with a pH value of more than $7$ is basic. Hence, according to the given pH values, solution ‘A’ is acidic in nature, while solution ‘B’ is basic. Also, since ‘A’ is acidic, it has a greater concentration of hydrogen ions.

22. What will happen if a solution of sodium hydrogen carbonate is heated? Give the equation of the reaction involved.

Ans: On heating, a solution of sodium hydrogen carbonate, sodium carbonate, carbon dioxide, and water are produced.

$\text{2NaHC}{{\text{O}}_{\text{3}}}\text{ + heat}\to \text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{ + C}{{\text{O}}_{\text{2}}}\text{ + }{{\text{H}}_{\text{2}}}\text{O}$

23. Write an equation to show the reaction between plaster of Paris and water.

Ans: The reaction is as follows: 

$\text{CaS}{{\text{O}}_{\text{4}}}\text{.}\dfrac{\text{1}}{\text{2}}{{\text{H}}_{\text{2}}}\text{O + }\dfrac{\text{3}}{\text{2}}{{\text{H}}_{\text{2}}}\text{O}\to \text{CaS}{{\text{O}}_{\text{4}}}\text{.2}{{\text{H}}_{\text{2}}}\text{O}$ 

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

Ans: The presence of small amounts of acid in rainwater aids the conduction of electricity. Distilled water is pure water and lacks ions. Therefore, it cannot conduct electricity.

25. Why do acids not show acidic behavior in the absence of water?

Ans: Acids produce hydrogen ions or hydronium ions only in presence of water. Therefore, it shows acidic behavior only in the presence of water.

26. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid is added to test tube A, while acetic acid is added to test B. In which test tube will the fizzing occur more vigorously and why?

Ans: The concentration of ${{\text{H}}^{\text{+}}}$  ions in test tube A will be more than that in test tube B because hydrochloric acid is stronger than acetic acid. Therefore, the faster reaction in test tube A will lead to vigorous fizzing.

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

Ans: Bacterial action on fresh milk turns it into curd. Hence, the lactose in the fresh milk is turned into lactic acid. Because of the formation of more acid, the pH will be lower than $6$.

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

Ans: A hard mass of gypsum is formed when the Plaster of Paris comes in contact with moisture. Therefore, it should be stored in a moisture-proof container.

29. Kazi and Priyam want to prepare dil ${{H}_{2}}S{{O}_{4}}$. Kazi added conc ${{H}_{2}}S{{O}_{4}}$ to water slowly with constant stirring & cooling whereas Priyam added water to conc ${{H}_{2}}S{{O}_{4}}$. Name the student who was correct and why?

Ans: The addition of water to concentrated acid leads to a highly exothermic reaction. The intensity of the heat produced can break the glass container or cause severe burns to the person adding it. On the other hand, adding acid to water with constant stirring aids the absorption of the heat produced by water and any harm/damage is avoided. Hence, Kazi was correct.

30. A first aid manual suggests that vinegar should be used to treat wasp sting and baking soda for bee stings.

1. What does this information tell you about the chemical nature of the wasp stings?

Ans:  Vinegar (acetic acid) is acidic in nature and it is to be used to heal or neutralize the effect of wasp stings, it implies that the chemical present in the stings is basic.

2. If there were no baking soda in the house, what other household substance could you use to treat bee stings?

Ans: Ammonium Hydroxide $\left( \text{N}{{\text{H}}_{\text{4}}}\text{OH} \right)$ can be used to treat bee stings

31. A compound ‘X’ on electrolysis in an aqueous solution produces a strong base. ‘Y’ along with two gases ‘A’ and ‘B’. ‘B’ is used in the manufacture of bleaching powder. Identify X, Y, A, and B. Write chemical equations.

Ans: The chemical equations may be written as:

$\text{2NaCl}\left( \text{aq} \right)\text{ + 2}{{\text{H}}_{\text{2}}}\text{O}\to \text{2NaOH}\left( \text{aq} \right)\text{ + C}{{\text{l}}_{\text{2}}}\left( \text{g} \right)\text{ + }{{\text{H}}_{\text{2}}}\left( \text{g} \right)$

Here,

$\text{X}\to \text{NaCl}$ 

$\text{Y}\to \text{NaOH}$ 

$ \text{A}\to {{\text{H}}_{\text{2}}} $

$ \text{B}\to \text{C}{{\text{l}}_{\text{2}}}$

32. A yellow powder X gives a pungent smell if left open in the air. It is prepared by the Reaction of dry compound Y with chlorine gas. It is used for disinfecting drinking water. Identify X and Y. Write the reaction involved.

Ans: The reaction is written as:

$\text{Ca}{{\left( \text{OH} \right)}_{\text{2}}}\text{ + C}{{\text{l}}_{\text{2}}}\to \text{CaOC}{{\text{l}}_{\text{2}}}\text{ + }{{\text{H}}_{\text{2}}}\text{O}$

Here,

$\text{X}\to \text{CaOC}{{\text{l}}_{\text{2}}}$

$\text{Y}\to \text{Ca}{{\left( \text{OH} \right)}_{\text{2}}}$

33. A few drops of phenolphthalein indicator were added to an unknown solution A. It acquired pink color. Now another unknown solution B was added to it drop by drop and the solution becomes colorless. Predict the nature of A & B.

Ans: Phenolphthalein turns pink in color when it is dissolved in a basic solution and the pink color becomes colorless on dissolution with an acid. Hence, according to the given question, we can say that solution ‘A’ is basic in nature, while solution ‘B’ is acidic.

3 Marks Questions

1. (a) Name the raw materials used in the manufacture of sodium carbonate by the Solvay process?

Ans: The raw materials used are- sodium hydroxide, limestone, and ammonia.

(b) How is sodium hydrogen carbonate separated from a mixture of $N{{H}_{4}}Cl$ and $NaHC{{O}_{3}}$?

Ans: Sodium hydrogen carbonate $\left( \text{NaHC}{{\text{O}}_{\text{3}}} \right)$ settles down as a precipitate because it is sparingly soluble in water. However, $\text{N}{{\text{H}}_{\text{4}}}\text{Cl}$ remains dissolved in the solution. The precipitate is removed by filtration.

2. Write equations for the following reactions

1. Dilute sulphuric acid reacts with zinc granules

Ans: The reaction can be written as:

$\text{Zn}\left( \text{S} \right)\text{ + }{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\left( \text{dil} \right)\to \text{ZnS}{{\text{O}}_{\text{4}}}\left( \text{aq} \right)\text{ + }{{\text{H}}_{\text{2}}}\left( \text{g} \right)$

2. Dilute hydrochloric acid reacts with magnesium ribbon.

Ans: The reaction can be written as:

$\text{Mg}\left( \text{S} \right)\text{ + 2HCl}\left( \text{dil} \right)\to \text{MgC}{{\text{l}}_{\text{2}}}\left( \text{aq} \right)\text{ + }{{\text{H}}_{\text{2}}}\left( \text{g} \right)$

3. Dilute sulphuric acid reacts with aluminum powder.

Ans: The reaction can be written as:

$\text{2Al}\left( \text{S} \right)\text{ + 3}{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\left( \text{dil} \right)\to \text{A}{{\text{l}}_{\text{2}}}{{\left( \text{S}{{\text{O}}_{\text{4}}} \right)}_{\text{3}}}\left( \text{aq} \right)\text{ + 3}{{\text{H}}_{\text{2}}}\left( \text{g} \right)$

3. (a) An aqueous solution has a pH value of $7.0$. Is this solution acidic, basic, or neutral?

Ans: The nature of the solution is neutral.

2. If ${{H}^{+}}$ concentration of a solution is $1\times 1{{0}^{-2}}$ mol ${{L}^{-1}}$ what will be its pH value?

Ans: It is given that, 

${{\text{H}}^{\text{+}}}\text{=1}\!\!\times\!\!\text{1}{{\text{0}}^{\text{-2}}}\text{ mol}\,{{\text{L}}^{\text{-1}}}$

Hence,

$\text{pH=log}\left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right]$

$ \text{=-log}\left[ {{\text{H}}^{\text{+}}} \right]$ 

 $\text{=-log}\left[ \text{1}{{\text{0}}^{\text{-2}}} \right]$ 

 $ \text{=-}\left( \text{-2} \right)\text{log10}$ 

Finally,

$\text{pH=2}$

(c) Which has higher pH value: $1-M\,\,HCl$ or $1-M\,\,NaOH$? 

Ans: A solution with $\text{1}\,\text{M}\,\,\text{NaOH}$ is basic in nature and will have a higher pH value.

A solution with $\text{1M}\,\,\text{HCl}$ is acidic in nature and will have a lower pH value.

4. What will you observe when:

1. Red litmus is introduced into a solution of sodium sulphate.

Ans:  No colour change will occur because the solution of $\text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}$ and water is almost neutral.

2. Methyl orange is added to dil $HCl$.

Ans:  The color of methyl Orange will change to reddish.

3. Blue litmus is introduced into a solution of ferric chloride

Ans: $\text{FeC}{{\text{l}}_{\text{3}}}$ solution will form ferric hydroxide and hydrochloric acid, when it reacts with water. The presence of a strong acid will make the solution acidic in nature. Therefore, the blue litmus will change to red.

5. A first aid manual suggests that vinegar should be used to treat wasp sting and baking soda for bee stings.

1. What does this information tell you about the chemical name of the wasp sting?

Ans: Vinegar (acetic acid) is acidic in nature and if it is to be used to heal or neutralize the effect of wasp stings, it implies that the chemical present in the stings is basic.

2. If there were no baking soda in the house, what other household substances would you use to treat as stings?

Ans: Baking soda is basic in nature. If it is used to treat bee stings, it implies that the stings must be acidic. In case of unavailability of baking soda in the house, a solution of ammonium hydroxide $N{{H}_{4}}OH$ can be used for the same.

6. Does Tartaric acid help in making a cake or bread fluffy. Justify.

Ans: No, tartaric acid does not make cake/bread fluffy because no carbon dioxide is released during baking. Its role is to react with the $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$ formed by the decomposition of $\text{NaHC}{{\text{O}}_{\text{3}}}$.

$ CH\left( OH \right)COOH+N{{a}_{2}}C{{O}_{3}}+CH\left( OH \right)COONa+{{H}_{2}}O+C{{O}_{2}} $

 $ \,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,| $

 $ CH\left( OH \right)COOH\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,CH\left( OH \right)COONa\, $

  Tartaric acid                                         Disod. Tartarate 

If this reaction does not occur, the $\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}$ will impart a bitter taste to the cake.

7. Explain why?

1. Common salt becomes sticky during the rainy season.

Ans: On exposure to moist air, common salt becomes sticky because it contains impurities of magnesium chloride, which has a tendency to become liquid.

2. Blue vitriol changes to white upon heating.

Ans: Blue vitriol $\left( \text{CuS}{{\text{O}}_{\text{4}}}\text{.5}{{\text{H}}_{\text{2}}}\text{O} \right)$ changes to anhydrous copper sulphate $\left( \text{CuS}{{\text{O}}_{\text{4}}} \right)$ on heating, which is white in colour.

8. A compound X of sodium is commonly used in the kitchen for making crispy pakoras. It is also used for curing acidity in the stomach. Identify ‘X’. What is its chemical formula?  State the reaction that takes place when it is heated during cooking?

Ans: Compound X can be identified as baking powder (or baking soda). Chemically, the compound is sodium hydrogen carbonate $\left( \text{NaHC}{{\text{O}}_{\text{3}}} \right)$. On heating the compound, the following reaction occurs:

$\text{2NaHC}{{\text{O}}_{\text{3}}}\xrightarrow{\text{heat}}\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\left( \text{s} \right)\text{ + }{{\text{H}}_{\text{2}}}\text{O}\left( \text{l} \right)\text{ + C}{{\text{O}}_{\text{2}}}\left( \text{g} \right)$

9. Explain why-

1. Anhydrous calcium chloride is used in desiccators

Ans: The hygroscopic nature of anhydrous calcium chloride makes it readily absorb moisture and therefore, it is used as a desiccator.

2. If a bottle full of concentrated ${{H}_{2}}S{{O}_{4}}$ is left open in the atmosphere by accident, the acid starts flowing out the bottle of its own.

Ans: Concentrated sulphuric acid is highly hygroscopic. It begins to absorb moisture from the air and gets diluted. Because of the increase in volume, the acid starts flowing out of the bottle.

10. How is plaster of Paris chemically different from gypsum? How may these be interconverted? Write one use of plaster of Paris?

Ans: Plaster of Paris is the anhydrous form of gypsum. It is prepared by heating gypsum. 

Plaster of Paris is used in surgical bandages for setting fractured bones. Before applying on the fractured bone, it is mixed with water, which results in hydration and it changes into gypsum. The hard mass of the gypsum keeps the bones in position.

Plaster of Paris and Gypsum may be interconverted by the reaction:

$CaS{{O}_{4}}\dfrac{1}{2}{{H}_{2}}O+\dfrac{3}{2}{{H}_{2}}O\to CaS{{O}_{4}}2{{H}_{2}}O$

Plaster of Paris                                Gypsum

11. (a) What is the action of red litmus on

1. Dry ammonia gas

Ans: As no hydroxyl ions are released, red litmus has no action on dry ammonia gas.

2. Solution of ammonia gas in water?

Ans: Ammonium hydroxide is formed when ammonia is passed through water. It turns red litmus blue because it dissociates to give hydroxyl ions.

(b) State the observations you would make on adding ammonium hydroxide to an aqueous solution of

1. ferrous sulphate

Ans: Double decomposition reaction gives a green precipitate of ferrous hydroxide.

$FeS{{O}_{4}}\left( aq \right)+2N{{H}_{4}}OH\left( aq \right)\to Fe{{\left( OH \right)}_{2}}+{{\left( N{{H}_{4}} \right)}_{2}}S{{O}_{4}}\left( aq \right)$

        (Green ppt.)

2. Aluminum chloride?

Ans: Double decomposition reaction gives a white precipitate of aluminum hydroxide.

$AlC{{l}_{3}}\left( aq \right)+3N{{H}_{4}}OH\left( aq \right)\to Al{{\left( OH \right)}_{3}}+3N{{H}_{4}}Cl\left( aq \right)$

        (White ppt.)

12. State the chemical property in each case on which the following uses of baking soda are based

1. As an antacid

Ans: The weakly alkaline nature of baking soda neutralizes the hydrochloric acid formed in the stomach.

$\text{NaHC}{{\text{O}}_{\text{3}}}\text{ + HCl}\to \text{NaCl + }{{\text{H}}_{\text{2}}}\text{O + C}{{\text{O}}_{\text{2}}}$

2. As a constituent of baking powder. Give the chemical for baking soda

Ans: Using baking soda while baking makes the cake porous and fluffy. It is because carbon dioxide gas is evolved in the form of bubbles when baking.

$\text{2NaHC}{{\text{O}}_{\text{3}}}\xrightarrow{\text{heat}}\text{N}{{\text{a}}_{\text{2}}}\text{C}{{\text{O}}_{\text{3}}}\text{ + }{{\text{H}}_{\text{2}}}\text{O + C}{{\text{O}}_{\text{2}}}$

The chemical formula of baking soda is $\text{NaHC}{{\text{O}}_{\text{3}}}$.

13. Metal compound ‘A’ 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.

Ans: We can say that ‘A’ is a salt of calcium because one of the products is calcium chloride.

The burning candle is extinguished, indicating the formation of carbon dioxide by the reaction of ‘A’ with hydrochloric acid.

Upon reaction with hydrochloric acid, calcium carbonate produces calcium chloride and carbon dioxide. Hence, ‘A’ is calcium carbonate.

The chemical equation can be given as:

$\text{CaC}{{\text{O}}_{\text{3}}}\text{ + HCl}\to \text{CaC}{{\text{l}}_{\text{2}}}\text{ + C}{{\text{O}}_{\text{2}}}\text{ + }{{\text{H}}_{\text{2}}}\text{O}$ 

14. Why do $\text{HCl,}\,\,\text{HN}{{\text{O}}_{\text{3}}}$ etc. show acidic characters in aqueous solution while solutions of compounds like alcohol and glucose do not show acidic character?

Ans: In their aqueous form, compounds like hydrochloric acid and nitric acid, release hydrogen ions, which signals acidic character.

On the other hand, compounds like alcohol and glucose cannot release hydrogen ions. Therefore, they show no acidic properties.

15. 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 ions concentration? Which is acidic and which one is basic?

Ans: On a pH scale, any solution having pH value less than $7$ is considered acidic and that with a pH value of more than $7$ is basic. Hence, according to the given pH values, solution ‘A’ is acidic in nature, while solution ‘B’ is basic. Also, since ‘A’ is acidic, it has a greater concentration of hydrogen ions.

16. Under what soil condition do you think a farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).

Ans: Quicklime (calcium oxide), slaked lime (calcium hydroxide), and chalk (calcium carbonate) are basic in nature. Hence, a farmer would use them to neutralize the effect of acidic soil conditions.

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

1. Why does he shift the pH of the milk from $6$ to slightly alkaline?

Ans:  Sodium hydrogen carbonate (baking soda) is a base. Hence, in addition to milk, the solution would become slightly alkaline. This implies that the pH value would become greater than $6$ (slightly alkaline) on the addition of a very small amount of baking soda.

2. Why does this milk take a long time to set a curd?

Ans: A neutralization reaction between the lactic acid of the curd and sodium hydrogen carbonate will prolong the time taken by milk to set as curd.

18. What is a neutralization reaction? Give two examples.

Ans: Neutralization reaction is the reaction between an acid and a base to produce salt and water. For example:

$ \text{NaOH + HCl}\to \text{NaCl + }{{\text{H}}_{\text{2}}}\text{O} $ 

$ \text{KOH + HN}{{\text{O}}_{\text{3}}}\to \text{KN}{{\text{O}}_{\text{3}}}\text{ + }{{\text{H}}_{\text{2}}}\text{O}$

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

Ans: The uses of washing soda are as follows:

1. Cleansing agent.

2. Permanently removing the hardness of the water.

3. Used in paper, glass, and soap industries.

The uses of baking soda are as follows:

1. Production of baking powder.

2. As an antacid.

20. Compound P forms enamel of teeth. It is the hardest substance of the body. It does not dissolve in water but it is corroded when pH in the mouth is below $5.5$. How does toothpaste prevent dental decay?

Ans: The compound P is $\text{Ca}_{\text{3}{{\left(\text{P}{{\text{O}}_{\text{4}}} \right)}_{\text{2}}}}$.

Bacterial action on the remaining food particles in the mouth produces acids from the degradation of sugar. Toothpaste is usually basic in nature. It helps in neutralizing the excess acid and prevents tooth decay.

21. The oxide of a metal M was water-soluble when a blue litmus strip was dipped in this solution, it did not go any change in color. Predict the nature of oxide.

Ans: The nature of the metal oxide is basic in nature. On dissolution in water, it forms a metal hydroxide. This hydroxide is basic in nature, as the blue litmus did not undergo any change in color.

$\text{MO + }{{\text{H}}_{\text{2}}}\text{O}\to \text{M}{{\left( \text{OH} \right)}_{\text{2}}}$

22. A road tanker carrying acid was involved in an accident and its contents spilled on the road, iron drain covers began melting and fizzing as the acid ran over them. A specialist was called to see if the acid actually leaked into the nearby river.

1. Explain how the specialist could carry out a simple test to see if the river water contains some acid or not.

Ans: The expert can use a simple litmus paper test to determine if the river water contains acid or not. If the expert dips a strip of blue litmus paper into the sample of river water and the color changes to red, it implies that the river water has been affected by the acid spill.

2. The word melting is incorrectly used in the report. Suggest a better name that should have been used.

Ans: The word melting can be replaced with corrosion.

3. Explain why drain covers began fizzing as the acid rain over them.

Ans: Hydrogen gas is evolved when iron reacts with an acid.

23. A compound ‘A’ on heating at $370K$ gives ‘B’ used as plaster for supporting defractured bones in the right position. ‘B’ on mixing with water changes to ‘A’. Identify ‘A’ and ‘B’ and write the chemical reaction.

Ans: The reaction can be given by:

$CaS{{O}_{4}}\dfrac{1}{2}{{H}_{2}}O+1\frac{1}{2}{{H}_{2}}O\to CaS{{O}_{4}}2{{H}_{2}}O$

Plaster of Paris                  Gypsum

     ‘B’                             ‘A’

24. A student heated a few crystals of copper sulphate in a dry boiling tube.

1. What will be the color of the copper sulphate after heating?

Ans: Copper Sulphate becomes white in color after heating.

2. Will you notice water droplets in the boiling tube?

Ans: Yes, water droplets will be present in the boiling tube.

3. Where have these come from?

Ans: Even though copper sulphate crystals seem to be dry, they contain water of crystallization. The water droplets are formed because of this water crystallization.

5 Marks Questions

1. (a) The pH of rainwater collected from two cities A and B was found to be $6$ and $5$ respectively. The water of which city is more acidic? Find out the ratio of hydrogen ion concentration in the two samples of rainwater?

Ans: Lower pH value is an indication of greater acidic nature. Hence, the rain water of city B is more acidic.

We know that,

  $ \text{pH=-log}\left[ {{\text{H}}^{\text{+}}} \right] $

 $ \text{=log}\left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right] $

For city A,

$\text{log}\left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right]\text{=6} $ 

 $ \left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right]\text{=anti log6} $ 

$ \text{=1}{{\text{0}}^{\text{6}}} $

 $ \left[ {{\text{H}}^{\text{+}}} \right]\text{=1}{{\text{0}}^{\text{-6}}} $

For city B,

$ \text{log}\left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right]\text{=5} $ 

$ \left[ \dfrac{\text{1}}{{{\text{H}}^{\text{+}}}} \right]\text{=anti log5=1}{{\text{0}}^{\text{5}}} $ 

 $ \left[ {{\text{H}}^{\text{+}}} \right]\text{=1}{{\text{0}}^{\text{-5}}}  $

Hence, the ratio is,

$\dfrac{\text{city}\,\text{A}}{\text{city}\,\text{B}}\text{=}\dfrac{\text{1}{{\text{0}}^{\text{-6}}}}{\text{1}{{\text{0}}^{\text{-5}}}} $ 

 $ \text{=}\dfrac{\text{1}}{\text{10}}  $

(b) Arrange the following in order (ascending) of their pH values.

$NaOH$ solution, Blood, lemon Juice.

Ans: The increasing order of pH values for the given solution is:

Lemon juice < Blood < $\text{NaOH}$ solution.

2. (a) Why does an aqueous solution of acid conduct electricity?

Ans: Water is a polarizing compound. In an aqueous solution form, acid dissociates to give ions. Electricity is conducted by the free movement of these ions.

2. How does the concentration of hydrogen ions ${{\left[ {{H}_{3}}O \right]}^{+}}$ change when the solution of an acid is diluted with water?

Ans: Dilution aids the process of dissociation of acid into ions. Thus, the concentration of ${{\left[ {{\text{H}}_{\text{3}}}\text{O} \right]}^{\text{+}}}$ ions increase on dilution.

3. Which has higher pH. A concentrated or dilute solution of $HCl$?

Ans: The number of ions per unit volume decreases with an increase in ${{\left[ {{\text{H}}_{\text{3}}}\text{O} \right]}^{\text{+}}}$ ions. Therefore, pH will increase on dilution.

4. What would you observe on adding dil $HCl$ acid to

1. Sodium bicarbonate is placed in a test tube.

Ans: A brick effervescence from the evolution of $\text{C}{{\text{O}}_{\text{2}}}$ is observed.

$\text{NaHC}{{\text{O}}_{\text{3}}}\left( \text{s} \right)\text{ + HCl}\left( \text{aq} \right)\to \text{NaCl}\left( \text{aq} \right)\text{ + C}{{\text{O}}_{\text{2}}}\left( \text{g} \right)\text{ + }{{\text{H}}_{\text{2}}}\text{O}\left( \text{aq} \right)$

2. Zinc metal in a test tube.

Ans: A brick effervescence from the evolution of ${{\text{H}}_{\text{2}}}$ is observed.

$\text{Zn}\left( \text{s} \right)\text{ + 2HCl}\left( \text{aq} \right)\to \text{ZnCl}\left( \text{aq} \right)\text{ + }{{\text{H}}_{\text{2}}}\text{O}\left( \text{g} \right)$

3. A road tanker carrying acid was involved in an accident and its contents spilled on the road. At the side of the road iron drain cover began melting and fizzing as the acid ran over them. A specialist was called to see if the acid actually leaked into the nearby river.

1. Explain why specialists could carry out sample tests to see if the river water contains some acid or not.

Ans: The expert can use a simple litmus paper test to determine if the river water contains acid or not. If the expert dips a strip of blue litmus paper into the sample of river water and the color changes to red, it implies that the river water has been affected by the acid spill.

2. Suggest a better report name for the word ‘melting’

Ans: The chemical reaction of drain cover (made of iron) with the acid can be called corrosion.

3. Explain why the drain covers began fizzing as the acid ran over them.

Ans: Hydrogen gas is evolved when iron reacts with an acid (like sulphuric acid or hydrochloric acid). The release of hydrogen is accompanied by effervescence and hence, the fizzing on the covers was observed.

4. Write word equations and then balanced equations for the reaction taking place when:

1. Dilute Sulphuric acid reacts with zinc granules.

Ans: Zinc + Sulphuric acid $\to $ Zinc sulphate + Hydrogen

$Zn+{{H}_{2}}S{{O}_{4}}\to ZnS{{O}_{4}}+{{H}_{2}}$

2. Dilute hydrochloric acid reacts with magnesium ribbon.

Ans: Magnesium + Hydrochloric acid $\to $Magnesium chloride + Hydrogen gas 

$Mg+{{2HCl}}\to MgC{{l}_{2}}+{{H}_{2}}$

3. Dilute Sulphuric acid reacts with aluminum powder

Ans: Aluminum + Sulphuric acid $\to $ Aluminum sulphate + Hydrogen gas 

$2Al+3{{H}_{2}}S{{O}_{4}}\to A{{l}_{2}}{{\left( S{{O}_{4}} \right)}_{3}}+3{{H}_{2}}$

4. Dilute hydrochloric acid reacts with iron filings.

Ans: Iron + Hydrochloric acid $\to $Iron chloride + Hydrogen

$Fe+{{2HCl}}\to FeC{{l}_{2}}+{{H}_{2}}$

5. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity

Ans: The following activity can prove that alcohol and glucose both contain hydrogen but are not categorized as acids.

Apparatus required: - Beaker, nails, battery, connecting wires, bulb, switch and alcohols. 

Procedure:

1. The experiment is set up as shown

2. Ethyl alcohol is taken in the beaker.

3. The bulb does not glow when the switch is in on position.

4. The alcohol is replaced with a glucose solution. The bulb still does not glow.

6. A compound X is bitter in taste. It is a component of washing powder & reacts with dil. $\text{HCl}$ to produce brisk effervescence due to colorless, odorless gas Y which turns lime water milky due to formation of Z. When an excess of is passed, milkiness

disappears due to the formation of P. Identify X, Y, And Z & P.

 Ans: The chemical reactions are as follows:

$ N{{a}_{2}}C{{O}_{3}}\left( s \right)\text{ }+\text{ }2HCl\left( aq \right)\to 2NaCl\left( aq \right)\text{ }+\text{ }{{H}_{2}}O\left( l \right)\text{ }+\text{ }C{{O}_{2}}\left( g \right) $

 $ Ca{{\left( OH \right)}_{2}}\left( aq \right)\text{ }+\text{ }C{{O}_{2}}\left( g \right)\to CaC{{O}_{3}}\left( s \right)\text{ }+\text{ }{{H}_{2}}O\left( l \right) $

 $ CaC{{O}_{3}}\left( s \right)\text{ }+\text{ }{{H}_{2}}O\left( l \right)\text{ }+\text{ }C{{O}_{2}}\left( g \right)\to Ca{{\left( HC{{O}_{3}} \right)}_{2}}\left( aq \right)$

Here,

$Ca{{\left( OH \right)}_{2}}$  is lime water

$CaC{{O}_{3}}$ 

is the white precipitate

And,

  $ X\to N{{a}_{2}}C{{O}_{3}} $

$Y\to C{{O}_{2}} $

 $ Z\to CaC{{O}_{3}} $

 $ P\to Ca{{\left( HC{{O}_{3}} \right)}_{2}} $ 

7. When gas passes through a saturated solution of ammoniacal brine, two compounds ‘X’ and ‘Y’ are formed. ‘Y’ is used as an antacid and decomposes to form another solid ‘Z’. Identify ‘X’, ‘Y’, ‘Z’ and write chemical equations.

Ans: The chemical reactions are as follows:

$NaC{{l}_{2}}+{{H}_{2}}O+C{{O}_{2}}+N{{H}_{3}}\to N{{H}_{4}}Cl+NaHC{{O}_{3}}$                                                    $2NaHC{{O}_{3}}\underrightarrow{heat}\,\,N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}$

(Sodium hydrogencarbonate)   (Sodium carbonate)

Here,

  $ X\to N{{H}_{4}}Cl $

 $ Y\to NaHC{{O}_{3}} $

 $ Z\to N{{a}_{2}}C{{O}_{3}} $

8. A substance ‘X’ is used in the kitchen for making tasty crispy pakoras and is also an Ingredient of antacid. Name the substance ‘X’.

1. How does ‘X’ help to make cakes and bread soft and spongy?

Ans: The chemical reaction is as follows:

$2NaHC{{O}_{3}}\underrightarrow{heat}\,\,N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}$

(Sodium hydrogen carbonate)   (Sodium carbonate)

The $C{{O}_{2}}$ gas escapes as bubbles, leaving behind pores. These pores make the cake/bread soft and spongy.

2. Is the pH value of the solution of ‘X’ is lesser than or greater than $\text{7}\text{.0}$?

Ans: Being salt of a strong base, the pH of the solution will be more than $7.0$.

Important Questions for Class 10 Science Chapter 2 - Free PDF Download

In the final examination of 10th board, around 3-4 questions are mandatorily asked from chapter acids, bases, and salts. Thus, there are maximum chances that students will score full marks from its questions. Students need good study material to prepare well and master it. Vedantu experts provide a free PDF for Class 10 Science Chapter 2 Important Questions. It is to ensure students need not search for study material from other websites.

The conceptual questions of Acids, Bases, and Salts need good practice. Hence, it is better if students try every question of this chapter. It is not that easy to get into a deep study of each concept. So we have a free PDF for Ch 2 Science Class 10 Important Questions for students that cover every concept as stated according to CBSE guidelines. There is a complete range of questions ranging from MCQs to subjective long-answer-type questions with maximum chances to be asked in the exams. However, students need to go through all topics and subtopics of this chapter to know their importance.

Ch 2 Science Class 10 Important Questions Concepts to Cover

The questions prepared in the PDF are from experts' knowledge and precisely according to CBSE guidelines. CBSE follows the pattern according to NCERT books and Acid Bases and Salts Class 10 Important Questions. However, know the important concepts covered under this chapter to prepare well and master it.

A Basic Introduction to Acids Bases and Salts

The fundamental introduction covers the knowledge of acids bases and salts that students have studied in previous classes. It includes the Litmus paper test, the taste of acid and base, and basic needs for these compounds in our day to day life.

Chemical Properties of Acids and Bases

Chemical properties for acid and base are tested in the school labs to find appropriate results. However, certain reactions are conducted to find the chemical properties of acids and bases. Some such properties are listed below.

• Acid and Bases Reacting with Metals

Students will perform experiments in the lab and write down reactions for an acid’s reaction and base with metal.

Acids react with metal and form salt along with Hydrogen gas.

Bases react with the metal to form salt and hydrogen gas.

• Acids and Bases Reaction with Each Other

Base along with acid together combine and react to form salt and water. It means it is the concept that the effect of acid nullifies if the base is added to it or vice versa.

• Acids Reacting with Metallic Oxides

Acid, along with metal oxides, will produce salt and water. Thus metal oxides are the basic oxides that produce salts when reacted with acid.

• Bases Reacting with Non-Metallic Oxides

When a base reacts with non-metallic oxide, it produces salt and water. It states that non-metallic oxides have acidic properties.

Common Properties of Acids and Bases

Acids and Bases in Water

Here students will learn about common properties that both base and acids show. One such common behaviour is in an aqueous form; both acids and bases can conduct electricity due to free ions. It is the common property between the two.

Strong and Weak Acids and Base

To find how strong are acids and bases, students will come across the concept of pH scale. The lesser pH value means more acidic the compound is. If pH value is 7, that means it is a neutral compound or acts as salt. If pH goes above 7, the compound starts showing basic properties. Thus more the pH value, more basic the compound is. Strength of acid goes down if it approaches near seven according to pH scale. Strength of a base increases if the pH value goes on increasing to 14.

More to Know About Salts

Here students encounter properties, formation, and uses of salts in our day to day life. The pH value of salts is generally ranging from 7 to 7.8. These are considered as neutral compounds (neither acidic nor basic).

Throughout the concept of Ch 2 Class 10 Science, students will be conducting certain experiments to note their final observations for the final compound formed. However, to remind them of the exams point of view, it could be challenging for them. Thus, acids bases and salts Class 10 Important Questions PDF can help them grow their concepts precisely.

Topics Covered in NCERT Class 10 Science Chapter 2 – Acid, Bases and Salts

Section 2.1 Understanding the Chemical Properties of Acids and Bases

• 2.1.1 Acids and Bases in the Laboratory

• 2.1.2 How do Acids and Bases React with Metals?

• 2.1.3 How do Metal Carbonates and Metal Hydrogen Carbonates React with Acids?

• 2.1.4 How do Acids and Bases React with each other?

• 2.1.5 Reaction of Metallic Oxides with Acids

• 2.1.6 Reaction of a Non-metallic Oxide with Base

Section  2.2 What Do All Acids and All Bases Have in Common?

• 2.2.1 What Happens to an Acid or a Base in a Water Solution? 

Section 2.3 How Strong are Acid or Base Solutions?

• 2.3.1 Importance of pH in Everyday Life

Section 2.4 More About Salts

• 2.4.1 Family of Salts 

• 2.4.2 pH of Salts

• 2.4.3 Chemicals from Common Salt

• 2.4.4 Are the Crystals of Salts Really Dry?

Important Questions of Acids Bases and Salts Class 10

Based on certain experiments conducted by students in their labs, a list of CBSE Class 10 Science Chapter 2 Important Questions are prepared. These questions are generally asked in the exams, and students need to be very precise in answering them. This chapter has the highest marks weightage, which can come in one mark, three marks, and five marks questions. Hence the PDF prepared carries different types of questions along with the answering pattern. Some of such Chapter 2 Science Class 10 Important Questions are listed below.

• How will you distinguish acids from bases for their chemical properties?

• What happens when an acid reacts with a metal? Explain with a suitable reaction example.

• Explain metallic oxides reacting with acids.

• Are non-metallic oxides acidic in nature? Justify your statement with suitable examples.

• Why should you not keep sour substances in copper or brass utensils?

• How can you say that acids in aqueous solution conduct electricity?

• Is it possible for dry HCl change the colour for dry litmus paper? If no, then why?

• Why is it good to add acids to water drop by drop rather than adding water to acids?

• State different chemical properties of bases. 

• What happens when excess base is diluted into the water? What happens to the present concentration of OH- ions?

• Suppose you have two compounds. One has pH as five another having 9. Which compound will be having more H+ ions? Also, describe which one is acidic or basic. Give reasons for each. 

• What happens to red litmus when kept in acid?

• How are salts formed?

• Which is common salt widely used?

All the Class 10 Science Ch 2 Important Questions stated above are most likely to be asked in the finals of 10th standard. These are crucial questions that students need to prepare well before exams for Ch 2 Class 10.

Benefits of Acid Bases and Salts Class 10 Important Questions

Students will come across various chemical properties of acids and bases in Ch 2 Class 10. However, the experimental results can make it challenging for them to prepare well for exams. Thus there is a need to work on Class 10th Science Chapter 2 Important Questions first. Know various features of having PDF for important questions of Acids Bases And Salts Class 10.

1. Practical Focus of Chapter 2: Chapter 2 of Class 10 is practical-based, requiring a strong command of concepts for effective coverage and preparation. Vedantu's expert-prepared PDF ensures comprehensive coverage of all essential concepts.

2. Application of Concepts in Real Life: Students will engage with diverse questions grounded in day-to-day life examples within the Acids, Bases, and Salts Class 10 Important Questions. This approach facilitates a precise understanding of each concept.

3. Reference Guides for Final Exams: These important questions serve as valuable reference guides, aiding students in thorough preparation for their final exams by aligning with the exam syllabus.

4. Accessible Language and Interactivity: The questions and answers are crafted in elementary and interactive language, promoting better understanding. This approach not only enhances comprehension but also contributes to scoring good grades and securing full marks in the questions posed.

Important Related Links for CBSE Class 10 Science