Study MaterialsNCERT SolutionsNCERT Solutions For Class 7 ScienceNCERT Solutions for Class 7 Science Chapter 5 Acid ,Bases And Salts

NCERT Solutions for Class 7 Science Chapter 5 Acid ,Bases And Salts

NCERT Solutions Class 7 Science Chapter 5 Updated for 2024-25

Subject specialists have designed NCERT solutions for Science Class 7 Chapter 5 which includes thorough solutions for reference. These  NCERT solutions are updated according to the latest CBSE syllabus for 2024-25 and are provided in easy language for understanding. Tips and tricks are also provided.
These solutions are provided so a student can clear his doubts and get help with deep understanding of the concept. Also you can refer them to make the chapter notes and revisions notes. PDF of this can also be downloaded from website.

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    Light Shadow and Reflection Class 7 Questions and Answers PDF

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      NCERT Class 7 Science Chapter 5 Questions and Answers

      1. State differences between acids and bases.

      Ans :

      Acids Bases

      1) They are sour in taste 1) They are bitter in taste

      2) They turn blue litmus to red 2) They turn red litmus to blue

      3) Generally acids give H+ ions when they 3) Generally bases give OH– ions when they

      dissolved in water Ex : Hydrochloric acid dissolve in water Ex ; Sodium Hydroxide (NaOH)

      (HCl), Sulphuric acid (H2SO4), Ammonium Hydroxide (NH4OH)

      Nitric acid (HNO3) etc… Calcium Hydroxide [Ca(OH)2] etc….

      2. Ammonia is found in many house hold products, such as window cleaners. It turns red litmus to blue. What is its nature?

      Ans : Ammonia turns red litmus to blue due to its basic nature.

      3. Name the source from which litmus solution is obtained. What is the use of this solution ?

      Ans : 1) Litmus solution is extracted from lichens.

      2) It has a mauve (purple) colour in distilled water.

      3) When added to an acidic solution, it turns Purple to Red.

      4) When added to a basic solution, it turns Purple to Blue.

      5) It is available in the form of a solution, (or) in the form of strips of paper known as litmus paper.

      4. Is the distilled water acidic / basic / neutral ? How would you verify it ?

      Ans : 1) The distilled water is neutral.

      2) Put a drop of distilled water on the strips of red and blue litmus papers, each with the help of a dropper.

      3) We observe that colour of the litmus paper is not changed.

      4) Water is neither acidic nor basic i.e., water is neutral.

      5. Describe the process of neutralisation with the help of an example.

      Ans : 1) The reaction between an acid and a base is known as neutralisation.

      2) Salt and water are produced in this process with the evolution of heat.

      Acid + Base Salt + Water

      (Heat is evolved)

      Ex : Hydrochloric acid + Sodium Hydroxide Sodium chloride + Water

      HCl + NaOH NaCl + H2O

      6. Mark ‘T’ if the statement is true and ‘F’ if it is false.

      Ans : i) Nitric acid turns red litmus blue (T/F) – False

      ii) Sodium hydroxide turns blue litmus red (T/F) – False

      iii) Sodium hydroxide and Hydrochloric acid neutralise each other and form salt and water

      (T/F) – True

      iv) Indicator is a substance which shows different colour in acidic and basic solutions (T/F) – True

      v) Tooth decay is caused by the presence of a base (T/F) – False

      7. Dorji has a few bottles of soft drink in his restaurant. But unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third wants neutral drink. How will Dorji decide which drink is to be served to whom ?

      Ans : 1) Dorji tests the nature of these few bottles of soft drink with litmus paper.

      2) Which soft drink bottle turns blue litmus to red i.e., acidic soft drink

      3) Which soft drink bottle turns red litmus to blue i.e., basic soft drink

      4) Which soft drink bottle does not change litmus paper i.e. neutral soft drink.

      5) Finally he distributed these three different Acidic, basic and neutral soft drink bottles
      individually to the customers.

      8. Explain why :

      a. An antacid tablet is taken when you suffer from acidity.

      Ans : 1) Our stomach contains Hydrochloric acid.

      2) It helps us to digest food.

      3) Too much of acid in the stomach causes indigestion some times. Indigestion is painful.

      4) To relieve indigestion, we take an antacid such as Milk of Magnesia, Which contains Magnesium hydroxide.

      5) It neutralises the effect of excessive acid.

      b. Calamine solution is applied on the skin when an ant bites.

      Ans : 1) The sting of an ant contains Formic acid.

      2) When an ant bites, it injects acidic liquid into the skin i.e, Formic acid.

      3) The effect of the acid can be neutralised by rubbing moist baking soda (Sodium hydrogen
      carbonate) or Calamine solution, Which contains Zinc carbonate.

      c. Factory waste is neutralised before disposing it into the water bodies.

      Ans : 1) The wastes of many factories contain acids.

      2) If they are allowed to flow into the water bodies those acids will kill fish and other organisms

      3) There fore the factory wastes are neutralised by adding basic substances.

      9. Three liquids are given to you. One is Hydrochloric acid, another is Sodium hydroxide and third is a sugar solution. How will you identify them ? You have only turmeric indicator ?

      Ans : Turmeric is a natural indicator present in yellow colour. In acidic medium it remains same, where as in basic medium turns to reddish brown colour.

      When we dip turmeric indicator into three test tubes containing HCl, NaOH and Sugar solution, in which test tube it turns to reddish brown it is NaOH. Then use the same Indicator and dip in remaining two solutions, in which test tube it turns back to yellow it is HCl and the remaining solution is sugar solution.

      10. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution ? Explain.

      Ans : The nature of the solution may be neutral or basic because the solutions which do not change the colour of blue litmus, are either neutral or basic.

      11. Consider the following statements.

      a) Both acids and bases change colour of all indicators.

      b) If an indicator gives a colour change with an acid, it does not give a change with a base.

      c) If an indicator changes colour with a base, it does not change colour with an acid.

      d) Change of colour in an acid and a base depends on the type of the indicator.

      Which of these statements are correct ?

      i) All four ii) a and b iii) b and c iv) only d

      Ans : iv) only d

      Important Topics Covered in Class 7 Science Chapter 5 Acids, Bases and Salts

      Acids and Bases

      • Acids are sour in taste and turn blue litmus paper red
      • Bases are bitter in taste, slippery to touch, and turn red litmus paper blue
      • Examples of acids: orange juice, curd, vinegar, hydrochloric acid
      • Examples of bases: soap, ammonium hydroxide, calcium hydroxide

      Natural Indicators

      • Litmus solution is extracted from lichens and used to test acidic or basic nature of solutions
      • Other natural indicators include turmeric, china rose, and red cabbage


      • Reaction between an acid and base to form salt, water, and heat
      • Acids and bases neutralize each other’s properties in this process
      • Example: HCl + NaOH → NaCl + H2O


      • Salts can be acidic, basic or neutral depending on the acid-base reaction
      • Common salt (NaCl) is a neutral salt formed from HCl and NaOH

      pH Scale

      • Used to measure acidity or basicity of a solution on a scale of 0-14
      • pH less than 7 is acidic, 7 is neutral, and greater than 7 is basic


      • Antacids like milk of magnesia used to reduce stomach acidity
      • Baking soda and vinegar used in cooking
      • Acids and bases used in manufacturing various products

      The combination of acid and base forms the salt which can either be acidic, basic or neutral in nature. This process is called as neutralisation. Neutralization is consider as most important for exams. To avoid confusion between acids, bases and salts students are advised to make tables for that.

      Overview of Infinite Learn Class 7 Science Chapter 5 NCERT Solutions

      Infinite Learn mission is to create world-class learning content for students. We are focussed on raising the students learning abilities. These Solutions have been structured very carefully to give several benefits to the students that utilize these study materials. That is why, these are crafted by subject matter experts to focus on concept and its explanation.

      For any type of support related to the NCERT Solutions for Class 7 given here, students can approach our support team who will help clear all their doubts. Students can also check out Infinite Learn for a more efficient learning experience.

      FAQs on Class 7 Science Chapter 5 Acid ,Bases And Salts

      What is the Salt Chemical Formula?

      The chemical formula for common salt is NaCl. It is made up of sodium (Na) and chlorine (Cl) ions.

      What are Acids, Bases, and Salts Examples Of?

      Acids, bases, and salts are examples of chemical compounds. They are substances formed when elements combine in specific ways. They have unique properties and reactions.

      What are the Formulas of Acids, Bases, and Salts?

      Acids: Hydrochloric acid: HCl Sulfuric acid: H₂SO₄ Acetic acid (vinegar): CH₃COOH Bases: Sodium hydroxide: NaOH Calcium hydroxide: Ca(OH)₂ Ammonium hydroxide: NH₄OH Salts: Common salt: NaCl Baking soda: NaHCO₃ Calcium carbonate: CaCO₃

      What are 5 Examples of Acids and Bases?

      Acids: Hydrochloric acid (HCl) Sulfuric acid (H₂SO₄) Acetic acid (CH₃COOH) Citric acid (found in citrus fruits) Lactic acid (found in sour milk) Bases: Sodium hydroxide (NaOH) Potassium hydroxide (KOH) Calcium hydroxide (Ca(OH)₂) Ammonium hydroxide (NH₄OH) Magnesium hydroxide (Mg(OH)₂)

      What is the Acid Formula?

      The formula for an acid can vary depending on the type of acid. For example, the formula for hydrochloric acid is HCl, and for sulfuric acid, it is H₂SO₄. What is Called Acid, Base, and Salt? Acid: A substance that tastes sour, turns blue litmus paper red, and releases hydrogen ions (H⁺) in solution. Base: A substance that tastes bitter, feels slippery, turns red litmus paper blue, and releases hydroxide ions (OH⁻) in solution. Salt: A compound formed when an acid reacts with a base, usually consisting of a positive ion from a base and a negative ion from an acid.

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