NCERT Solutions for Class 7 Science Chapter 5 Acids Bases and Salts

NCERT Solutions for Class 7 Science Chapter 5 Acids Bases and Salts

NCERT Solutions for Class 7 Science Chapter 5 Acids Bases And Salts: Generally acids are sour in taste and bases have a bitter taste and are soapy in touch. To test whether the given substances are acid, base or salt, indicators are used. Concepts can be better understood with the help of the NCERT solutions of Class 7 Science chapter 5 Acids Bases and Salts. The concept of neutralisation and their applications in daily life is one of the important topics of the NCERT Science chapter 5. There are a total of 11 questions explained in the NCERT solutions for class 7 science chapter 5 acids bases and salts. Practising the questions from NCERT solutions helps in scoring good marks in the exams. Students are recommended to go through NCERT Solutions for Class 7 to score high marks in their examination. Refer to the NCERT Class 7 Science Syllabus to know the exam pattern and important topics.

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NCERT Solutions for Class 7 Science Chapter 5 Acids Bases and Salts Exercise:

1. State differences between acids and bases.

Answer: Differences between acids and bases are given below:

Acids Bases
1 Turns blue litmus paper to red Turns red litmus paper to blue
2 They are sour in test They are bitter in test
3 Acids do not change the colour of turmeric indicator They change the colour of turmeric indicator
4 They are not soapy in touch They are soapy in touch
5 Eg:- HCL Eg:- NaOH

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

Answer: Bases turn the colour of red litmus to blue and as ammonia also turns the colour of red litmus to blue.
Therefore, ammonia is basic in nature

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

Answer: Litmus solution is commonly obtained from lichens. A natural dye which is extracted from lichens is dissolved in distilled water to form a litmus solution. Litmus solution is used as an indicator to distinguish between acids and bases.

When we add an acidic solution to it, it turns red and when we add a basic solution to it, it turns blue.

4. Is the distilled water acidic/basic/neutral?

How would you verify it?

Answer: Nature of distilled water is neutral. Because when we will test it with a litmus paper it does not change the colour of it and turns neither into red nor in blue colour.
Therefore, we can say that distilled water is neutral in nature.

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

Answer: The reaction between an acid and a base is known as neutralization reaction. In such type of reactions, acid and base reacts with each other and cancel out each other's effect and formation of salt and water takes place and energy in the form of heat is evolved.

For eg.
Sodium hydroxide reacts with hydrochloric acid to give sodium chloride and water with evo of some heat..

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

(i) Nitric acid turn red litmus blue. (T/F)

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

(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)

(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)

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

Answer: (i) FALSE

(ii) FALSE

(iii) TRUE

(iv) TRUE


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 one wants neutral drink. How will Dorji decide which drink is to be served to whom?

Answer: If Dorji has litmus paper or solution then with the help of that he can distinguish between them by putting one drop of each drink on litmus paper. If the colour of the litmus paper changes to blue, then it is a basic drink and if the colour of the litmus paper changes to red, then it is an acidic drink and if no change in colour then it is neutral.
Another method is he can distinguish between them by tasting the drinks. Drink with sour taste is acidic whereas drink with bitter taste is basic and neutral drinks will have no taste.

8 (a). Explain why:

An antacid tablet is taken when you suffer from acidity.

Answer: This is because antacids are the substance that neutralizes the excess of acids which is produced in the stomach during acidity as it contains a base, such as milk of magnesia.

These bases react with the excess amount of acids and neutralize their effect and giving us relief.

8 (b). Explain why:

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

Answer: The sting of an ant contains formic acid. Therefore, when an ant bites, it injects formic acid into our skin and due to which we feel a burning sensation. Calamine solution contains zinc carbonate which is basic in nature.

Therefore, when we applied it on the skin it neutralizes the effect of formic acid.

8 (c). Explain why:

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

Answer: Wastes materials in factories contain acids. Therefore, if we threw them directly into water bodies then the water becomes acidic and harm aquatic lives.

Therefore, these factory wastes are neutralized with basic chemicals before disposing to water bodies.

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.

Answer: When we place turmeric solution in contact with bases it turns into red colour and generally It is not affected by acids and neutral substances.

Now, we can distinguish between hydrochloric acid, sodium hydroxide and a sugar solution by applying turmeric solution to three test tubes, we will observe that

(1) test tube A (Hydrochloric acid) : No change in colour will take place because turmeric is not affected by acids.

(2) test tube B (sodium hydroxide) : Turmeric solution will change its colour to red because turmeric solution changes its colour to red when we place it in contact with bases.

(3) test tube c (sugar solution): No change in color will take place because sugar solution is neither basic nor acidic in nature
Therefore, we are only able to identify basic solution using turmeric as an indicator

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

Answer: We know that blue litmus paper turns into red colour when coming in contact with an acidic solution and basic and neutral solutions do not change the colour of blue litmus paper. Since blue litmus paper remains blue after it is dipped in a solution.

Therefore, the solution is either basic or neutral in nature.

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 d

(iii) b, c and d

(iv) only d

Answer: Out of all these only

(iv) only (d) is correct

Acids, Bases And Salts Class 7 Science Chapter 5-Topics

  • Acids and Bases
  • Natural Indicators Around Us
  • Litmus: a Natural Dye
  • Turmeric is Another Natural Indicator
  • China Rose as an Indicator
  • Neutralisation
  • Neutralisation in Everyday Life
  • Indigestion
  • Ant Bite
  • Soil Treatment
  • Factory Wastes

Chapterwise NCERT Solutions of Class 7 Science

Chapter 1Nutrition in Plants
Chapter 2Nutrition in Animals
Chapter 3Fibre to Fabric
Chapter 4Heat
Chapter 5Acids, Bases and Salts
Chapter 6Physical and Chemical Changes
Chapter 7Weather, Climate and Adaptations of Animals to Climate
Chapter 8Winds, storms and cyclones
Chapter 9Soil
Chapter 10Respiration in Organisms
Chapter 11Transportation in Animals and Plants
Chapter 12Reproduction in Plants
Chapter 13Motion and Time
Chapter 14Electric Current and its Effects
Chapter 15Light
Chapter 16Water: A Precious Resource
Chapter 17Forests: Our Lifeline
Chapter 18Wastewater Story

NCERT Solutions for Class 7 Subject Wise

NCERT Solutions for Class 7 Maths
NCERT Solutions for Class 7 Science

Benefits of NCERT Solutions for Class 7 Science Chapter 5 Acids Bases And Salts:

  • Testing using indicators is an important topic of the chapter. To familiarise with this concept there are many questions discussed in the NCERT solutions for Class 7 Science chapter 5 Acids Bases and Salts.
  • The NCERT solutions for Class 7 Science chapter 5 Acids Bases and Salts help students to solve homework problems of the chapter.