CBSE Class 10 Science Chapter 2 Acid, Bases and Salts Important Questions

Chapter 2 of CBSE Class 10 Science, Acids, Bases and Salts, is one of the most important chapters for board exams. Students often look for acid bases and salts class 10 important questions with answers so that they can practice well and understand the concepts in detail. This chapter deals with the everyday uses of acids, bases and salts, their reactions, properties, and applications in daily life. Having a clear understanding of the theory is essential, but practicing acid bases and salts class 10 extra questions and acid bases and salts class 10 questions and answers helps students gain more confidence.

The chapter introduces acids and bases in simple terms, explains the concept of pH, and then shows how different salts are formed from neutralization reactions. To prepare effectively, students must go through acids bases and salts class 10 important question banks and solve them regularly. These acid base and salt important question sets usually cover definitions, examples, balanced equations, uses, and applications in daily life. Questions can range from writing chemical reactions to explaining real-life examples like why curd is not kept in copper vessels or how antacids work.

Practicing class 10 acids bases and salts important questions not only strengthens concepts but also prepares students for exam-oriented writing. Teachers often stress solving acid bases and salts class 10 extra question practice sheets because they give exposure to tricky problems. Students should also focus on questions on pH class 10 since the pH scale is a central part of this chapter.

Another helpful way to revise is by using acid base and salts class 10 important question with answer booklets or notes prepared by experts. These guides allow students to quickly recall the formulas, properties, and equations needed. Repeatedly solving class 10 acid base and salt important question papers ensures that students are not surprised during the final exam. Since the board exam often repeats patterns, learning from acid and base class 10 important questions gives a strong edge.

Do Check: CBSE Class 10 Science Important Questions

Acid Bases and Salts Class 10 Important Questions with Answers (1 Marks)

Ques: Name the acids found in 

(i) Tomato

(ii) Vinegar

(iii) Tamarind.

Ans: (i) Tomato contains oxalic acid. (ii) Vinegar contains acetic acid. (iii) Tamarind contains tartaric acid.

Ques: You need to mix 15 mL of water and 10 mL of sulfuric acid.

(i) What is the correct method and why?

(ii) What is the name of this process?

Ans: (i) Pour the acid slowly into the water while stirring. This prevents dangerous splashing because the mixing releases a lot of heat.

(ii) This is called dilution of the acid.

Ques: How do antacids work?

Ans: When there is too much hydrochloric acid in the stomach, antacids (which are mild bases) neutralize the excess acid and relieve the burning and pain.

Ques: (a) What are olfactory indicators? Name two.

(b) From CH₃COOH, H₂SO₄, H₂CO₃, and HNO₃, which are strong acids?

Ans: (a) Olfactory indicators are substances whose smell changes in acidic or basic solutions. Onion and vanilla are examples.

(b) Sulfuric acid (H2SO₄) and nitric acid (HNO₃) are strong; acetic acid (CH₃COOH) and carbonic acid (H₂CO₃) are weak.

Ques: A white powder supports broken bones in casts.

(a) What is its name and formula?

(b) What happens when it is mixed with water?

Ans: (a) It is Plaster of Paris, calcium sulfate hemihydrate (CaSO₄·½H2O).

(b) It reacts with water and sets into hard gypsum (calcium sulfate dihydrate).

Ques: Describe what happens when dilute hydrochloric acid reacts with 

(i) magnesium ribbon

(ii) sodium hydroxide 

(iii) crushed eggshells.

Ans: (i) With magnesium, it forms magnesium chloride and hydrogen gas.

(ii) With sodium hydroxide, it neutralizes to form sodium chloride and water.

(iii) Eggshells (calcium carbonate) form calcium chloride, carbon dioxide, and water.

Ques: Give reasons:

(i) Why does tap water conduct electricity but distilled water does not?

(ii) Why doesn’t dry hydrogen chloride turn blue litmus red, while dilute hydrochloric acid does?

(iii) Why do milk sellers sometimes add a little baking soda in summer?

(iv) Why do we add acid to water and not water to acid?

(v) Why is ammonia a base even though it has no hydroxyl group?

Ans: (i) Tap water has dissolved ions; distilled water lacks ions.(ii) Dry hydrogen chloride has no ions; in water it produces ions that show acidity.

(iii) Baking soda slows souring by resisting the formation of lactic acid.

(iv) Adding acid to water controls the intense heat released and avoids splashing.

(v) Ammonia produces hydroxide ions when dissolved in water, making the solution basic.

Do Check: NCERT Solutions for Class 10 Science

Ques: (a) Give the formulas for hydrated and anhydrous copper sulfate.

(b) Briefly describe how to convert between them.

Ans: (a) Hydrated copper sulfate is CuSO₄·5H₂O (blue). Anhydrous copper sulfate is CuSO₄ (white).

(b) Heating the blue crystals removes water and turns them white; adding water back restores the blue crystals.

Ques: (a) On what properties are these uses of baking soda based: as an antacid, in a soda–acid fire extinguisher, and in baking?

(b) How is washing soda obtained from baking soda?

Ans: (a) As an antacid, it is mildly basic and neutralizes stomach acid; with acid it releases carbon dioxide that helps extinguish flames; when heated in dough it releases carbon dioxide that makes food soft and spongy.

(b) Heat baking soda to make sodium carbonate, then crystallize it with water to form washing soda (sodium carbonate decahydrate).

Ques: Name natural sources of these acids: citric, oxalic, lactic, tartaric.

Ans: Citric acid—lemons and oranges; oxalic acid—tomatoes and guava; lactic acid—sour milk or curd; tartaric acid—tamarind.

Ques: Four solutions have pH 11, 5, 7, and 2. Predict their nature.

Ans: pH 11 is basic; pH 5 is acidic; pH 7 is neutral; pH 2 is strongly acidic.

Ques: (i) What is baking powder made of?

(ii) Why do cakes and bread rise when baking powder is used?

Ans: (i) Sodium hydrogen carbonate (baking soda) and a mild acid such as tartaric acid.

(ii) They react to release carbon dioxide gas, which makes the batter or dough rise and become fluffy.

Ques: Two equal magnesium ribbons are placed in separate tubes. One gets sulfuric acid; the other gets carbonic acid.

(a) Which reacts more vigorously?

(b) Why?

(c) What gas is produced and how do you test it?

(d) Write the reactions in words.

(e) Which acid has lower pH and which has lower hydrogen ion concentration?

Ans: (a) The tube with sulfuric acid.

(b) Sulfuric acid is a strong acid; carbonic acid is weak.

(c) Hydrogen gas is produced; it gives a “pop” sound with a burning splinter.

(d) Magnesium + sulfuric acid → magnesium sulfate + hydrogen; magnesium + carbonic acid → magnesium salt (carbonate/bicarbonate) + hydrogen.

(e) Sulfuric acid has lower pH; carbonic acid has lower hydrogen ion concentration.

Ques: How do you test the gas released when hydrochloric acid reacts with an active metal?

Ans: Bring a burning matchstick near it; if it burns with a “pop,” the gas is hydrogen.

Ques: (a) What are bases that dissolve well in water called? Give one example.

(b) How is tooth decay linked to pH, and how can it be prevented?

(c) Why does a bee sting hurt, and how does baking soda help?

Ans: (a) Alkalis; example: sodium hydroxide.

(b) Low pH (acidic conditions) attacks tooth enamel; brushing and using slightly basic toothpaste helps neutralize acids.

(c) The sting injects formic acid; baking soda neutralizes the acid and reduces pain.

Do Check: CBSE Class 10 Science Sample Papers

Ques: A white powder is added when baking to make breads and cakes soft and fluffy. Name it, list its main ingredients, explain each role, and state what happens on heating.

Ans: It is baking powder. It contains baking soda and a mild acid (like tartaric acid). Baking soda releases carbon dioxide on heating to make the mixture rise; the acid prevents a bitter taste by reacting with any leftover soda.

Ques: “Sodium hydrogen carbonate is a basic salt”—justify. How is it converted to washing soda?

Ans: It is made from a strong base (sodium hydroxide) and a weak acid (carbonic acid), so its solution is basic. Heating it gives sodium carbonate, which can be crystallized to washing soda.

Ques: Describe an activity showing that acids react with metal carbonates or bicarbonates to produce carbon dioxide. Write the reactions in words and name two natural forms of calcium carbonate.

Ans: Put marble chips (calcium carbonate) in a flask and add dilute acid; pass the gas into limewater. Limewater turns milky, showing carbon dioxide is present. If more carbon dioxide is passed in, the milkiness clears. 

Word reactions: calcium carbonate + acid → calcium salt + carbon dioxide + water; 

limewater + carbon dioxide → calcium carbonate + water (milky); 

calcium carbonate + carbon dioxide + water → calcium hydrogen carbonate (clear). 

Natural forms: marble and limestone (also chalk).

Ques: (a) Which acid and base together make common salt? Give its name, formula, and source.

(b) What is rock salt?

(c) What happens when electricity passes through brine?

Ans: (a) Hydrochloric acid and sodium hydroxide make sodium chloride (NaCl), obtained from sea water and salt deposits.

(b) Rock salt is the mineral halite (impure sodium chloride), often white, bluish, or yellowish.

(c) Electrolysis produces hydrogen gas, chlorine gas, and sodium hydroxide solution.

Acid Bases and Salts Class 10 Extra Questions (2 Marks)

Ques: (i) Why is hydrochloric acid called a strong acid and acetic acid a weak acid? How can this be checked?

(ii) Why does an acid solution conduct electricity?

(iii) Four solutions have pH 6, 9, 12, and 7.

(a) Which is most acidic and which is most basic?

(b) Arrange them from lowest to highest hydrogen ion concentration.

(c) How will pH paper change in solutions with pH 12 and pH 7?

Ans: (i) Hydrochloric acid ionizes almost completely; acetic acid ionizes only partly. You can check by stronger conductivity and pH color with HCl.

(ii) Acids produce ions in water, which carry charge.

(iii) (a) Most acidic: pH 6; most basic: pH 12.

(b) From lowest to highest hydrogen ion concentration: pH 12, pH 9, pH 7, pH 6.

(c) pH 12 turns the paper blue/purple (basic); pH 7 shows a neutral green.

Ques: (i) A base called X absorbs moisture and is made by the chlor–alkali process. Name it and write the overall process in words.

(ii) What type of reaction happens when X reacts with dilute hydrochloric acid?

(iii) Why must acid be added to water during dilution?

Ans: (i) X is sodium hydroxide. In the chlor–alkali process, brine is electrolyzed to produce sodium hydroxide solution, hydrogen gas, and chlorine gas.

(ii) Neutralization: sodium hydroxide reacts with hydrochloric acid to give sodium chloride and water.

(iii) The mixing is highly exothermic; adding acid to water controls heat and prevents splashing.

Ques: A student adds marble to dilute hydrochloric acid and sends the gas into limewater. What is seen, and what if excess gas is passed? Explain in words.

Ans: Limewater first turns milky due to calcium carbonate formation. With excess carbon dioxide, it becomes clear as calcium hydrogen carbonate forms.

Ques: (a) Name the yellowish–white calcium compound used to disinfect drinking water, give its chemical name and formula, and say how it is made. Mention two other uses.

(b) Write the overall chlor–alkali process in words.

Ans: (a) Bleaching powder, calcium oxychloride (CaOCl₂). It is made by passing dry chlorine over slaked lime. Uses: bleaching textiles and paper; disinfecting water.

(b) Electrolysis of brine produces sodium hydroxide solution, hydrogen gas, and chlorine gas.

Ques: (a) What pH range suits our body? How do antacids help? Name one antacid.

(b) Fresh milk has pH 6. What happens to pH when it becomes curd?

(c) Why does adding a little baking soda make milk take longer to set as curd?

(d) What is the nature of toothpastes and how do they prevent tooth decay?

Ans: (a) Body fluids function best around neutral (about pH 7–7.8; the stomach is acidic). Antacids neutralize extra stomach acid; one example is sodium hydrogen carbonate.

(b) The pH decreases because curd is more acidic.

(c) It makes the milk slightly basic, slowing the bacteria that form lactic acid.

(d) Toothpastes are mildly basic; they neutralize acids that would attack enamel.

Ques: (a) Name and explain the crystals that turn white on heating but become blue again on cooling.

(b) Which compound has ten water molecules per formula unit? How is it prepared and used?

Ans: (a) Blue crystals of hydrated copper sulfate (CuSO4·5H2O) lose water on heating and turn white; they regain blue color by absorbing water again.

(b) Washing soda (sodium carbonate decahydrate, Na2CO3·10H2O). It is made by heating baking soda to sodium carbonate and then crystallizing. Uses include making washing powder and glass.

Ques: (a) Write, in words, what happens when an acid reacts with:

(i) a metal carbonate, (ii) a metal bicarbonate, and (iii) a metal oxide.

(b) Three solutions have pH 2, 10, and 13. Which has the highest hydrogen ion concentration, and what is the nature of each solution?

Ans: (a) (i) Acid + metal carbonate → salt, carbon dioxide, and water.

(ii) Acid + metal bicarbonate → salt, carbon dioxide, and water.

(iii) Acid + metal oxide → salt and water (neutralization).

(b) The pH 2 solution has the highest hydrogen ion concentration. pH 2 is acidic, pH 10 is basic, pH 13 is strongly basic.

Do Check: CBSE Class 10 Science Syllabus

Ques: (a) A metal compound X reacts with dilute sulfuric acid to release bubbles; one product is calcium sulfate. Name X and the gas formed, and state the reaction in words.

(b) (i) Name one antacid and how it helps. (ii) A farmer adds quicklime or calcium carbonate to soil. What does this mean about the soil and why is it done?

Ans: (a) X is calcium carbonate; the gas is carbon dioxide. In words: calcium carbonate + dilute sulfuric acid → calcium sulfate, carbon dioxide, and water.

(b) (i) Sodium hydrogen carbonate; it neutralizes extra stomach acid. (ii) The soil is acidic; adding a base reduces acidity for better crop growth.

Ques: What is the difference between strong and weak acids? From the list—hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, and sulfuric acid—separate strong and weak acids.

Ans: Strong acids ionize almost completely in water; weak acids ionize only partly. Strong: hydrochloric, nitric, sulfuric. Weak: citric, acetic, formic.

Ques: Give the chemical name of Plaster of Paris and the reaction it undergoes with water, in words.

Ans: Plaster of Paris is calcium sulfate hemihydrate. When mixed with water, it turns into gypsum (calcium sulfate dihydrate) and hardens.

Ques: Briefly explain how washing soda is prepared from baking soda; give the reactions in words.

Ans: Heating baking soda forms sodium carbonate, which is then crystallized with water to make washing soda crystals.

Ques: What is the color of crystals of iron(II) sulfate heptahydrate, and how does the color change on heating?

Ans: They are pale green. On heating, they lose water and turn whitish; further heating can produce brown iron(III) oxide with sulfur oxides.

Ques: Classify these salts as acidic, basic, or neutral: potassium sulfate, ammonium chloride, sodium carbonate, and sodium chloride.

Ans: Neutral: potassium sulfate and sodium chloride. Acidic: ammonium chloride. Basic: sodium carbonate.

Ques: When carbon dioxide is passed into limewater, what change is seen? State the change in words.

Ans: Limewater turns milky because insoluble calcium carbonate forms.

Ques: (a) What is a universal indicator?

(b) How is sodium hydroxide prepared in industry—name the process and describe it in words.

Ans: (a) A universal indicator is a mixture of indicators that shows a wide range of pH through different colors.

(b) In the chlor–alkali process, brine is electrolyzed to produce sodium hydroxide solution, hydrogen gas, and chlorine gas.

Ques: A gas X reacts with lime to form a compound Y used for bleaching. Identify X and Y and describe the reaction in words.

Ans: X is chlorine; Y is bleaching powder (calcium oxychloride). Dry chlorine reacts with slaked lime to form bleaching powder and water.

Ques: (i) Name the compound obtained from baking soda that removes permanent hardness of water.

(ii) Give its formula.

(iii) What happens on recrystallization from water?

Ans: (i) Sodium carbonate.

(ii) Na2CO3.

(iii) It forms washing soda, sodium carbonate decahydrate.

Acids Bases and Salts Class 10 Important Questions (3 Marks)

Ques: What is a neutralization reaction? Give two examples in words.

Ans: Neutralization is when an acid reacts with a base to form salt and water. Examples: hydrochloric acid + sodium hydroxide → sodium chloride + water; sulfuric acid + potassium hydroxide → potassium sulfate + water.

Ques: What is tooth enamel made of? When does it start to corrode, and why do dentists suggest toothpaste or tooth powder?

Ans: Enamel is mainly calcium phosphate. It corrodes in acidic conditions caused by bacterial acids from food. Toothpaste or tooth powder is slightly basic and neutralizes these acids to protect teeth.

Ques: What is Plaster of Paris chemically? How is it prepared, and give two uses.

Ans: It is calcium sulfate hemihydrate. It is made by heating gypsum to remove part of its water. Uses: making chalk and making casts or molds (including medical casts).

Ques: What is baking soda chemically called? How is it prepared in general, and give one use.

Ans: It is sodium hydrogen carbonate. It is prepared from brine, ammonia, and carbon dioxide (Solvay-type route). It is used as an antacid and in baking.

Ques: (a) What is an alkali? Give one example.

(b) Why do hydrochloric acid and nitric acid show acidic behavior in water, while alcohol and glucose do not?

Ans: (a) An alkali is a base that dissolves well in water; example: sodium hydroxide.

(b) Strong acids ionize to give hydrogen ions in water; alcohol and glucose do not produce ions, so they are not acidic.

Ques: Show by an activity that substances like alcohol and glucose contain hydrogen but are not acids.

Ans: Set up a simple conductivity circuit with two nails and a battery. Solutions of alcohol or glucose do not light a bulb because they do not produce ions in water. Therefore, having hydrogen does not automatically make a substance acidic.

Ques: A vegetable soup has pH 6.5. How will it taste?

Ans: Slightly sour, because it is mildly acidic.

Ques: Which bases are called alkalies? Give an example.

Ans: Water-soluble bases are called alkalies; for example, sodium hydroxide.

Ques: Describe in words what happens when sodium carbonate reacts with hydrochloric acid.

Ans: Sodium carbonate reacts with hydrochloric acid to produce sodium chloride, carbon dioxide, and water.

Do Check: CBSE Class 10 Science Notes

Ques: Give a word equation for any neutralization reaction and mention the states in general terms.

Ans: An aqueous acid reacts with an aqueous base to give an aqueous salt and liquid water; for example, nitric acid solution reacts with potassium hydroxide solution to form potassium nitrate solution and water.

Ques: What happens when chlorine is passed over slaked lime at about 313 K? Give two uses of the product.

Ans: Bleaching powder is formed. It is used to disinfect drinking water and to bleach textiles and paper.

Ques: What is the color change of red litmus in a solution of sodium carbonate?

Ans: It turns blue, showing the solution is basic.

Ques: Which gas is released when sodium hydrogen carbonate reacts with dilute hydrochloric acid?

Ans: Carbon dioxide gas.

Ques: Why should curd and sour foods not be kept in copper or brass vessels?

Ans: The acids in them react with these metals to form poisonous salts that are harmful.

Ques: Which gas is usually released when a dilute acid reacts with a metal, and what happens when you bring a flame near it?

Ans: Hydrogen gas is released; it burns with a “pop” sound.

Ques: What happens to pH if the concentration of hydrogen ions in a solution increases?

Ans: The pH decreases.

Ques: Which has a higher concentration of hydrogen ions: one-molar hydrochloric acid or one-molar acetic acid, and why?

Ans: One-molar hydrochloric acid, because it ionizes almost completely; acetic acid ionizes only partly.

Ques: Which gas is generally released when dilute hydrochloric acid reacts with an active metal?

Ans: Hydrogen gas.

Ques: What is the color of litmus in ammonium hydroxide solution?

Ans: Red litmus turns blue.

Ques: What is meant by “water of crystallization”? Describe an activity showing that blue copper sulfate has it.

Ans: Water of crystallization is water built into the crystal structure of a compound. When blue copper sulfate crystals are heated, they lose this water and turn white; adding water back restores the blue color.

Ques: A compound made from gypsum hardens when mixed with the right amount of water.

(i) Identify the compound.

(ii) Write its preparation in words.

(iii) State one important use.

Ans: (i) Plaster of Paris.

(ii) Heating gypsum removes some water to form Plaster of Paris.

(iii) It is used to make casts and molds, including surgical casts.

Ques: Name the products formed when:

(a) Hydrochloric acid reacts with caustic soda.

(b) Granulated zinc reacts with caustic soda in water.

(c) Carbon dioxide is passed into limewater.

Ans: (a) Sodium chloride and water.

(b) Sodium zincate and hydrogen gas.

(c) Calcium carbonate (milky) and water.