Chapter 4 Acids, Bases and Salts Question/Answers Important Word

Important terms to Learn In while learning Acids, Bases and Salts in Short Words:

Acid – A substance that tastes sour and turns blue litmus paper red. (अम्ल)
Acidic – Having the properties of an acid. (अम्लीय)
Base – A substance that tastes bitter and turns red litmus paper blue. (क्षार)
Basic – Having the properties of a base. (क्षारीय)
Indicator – A substance that changes color to show the presence of an acid or base. (संकेतक)
Neutral – Neither acidic nor basic; having a pH of 7. (तटस्थ)
Neutralisation – The reaction between an acid and a base to form a neutral solution. (उदासीनीकरण)
Salt – A compound formed from the reaction between an acid and a base. (लवण)

Exercise Question With Answers:👉

1. State differences between acids and bases.

Property	Acids	Bases
Taste	Sour	Bitter
Touch	Can be corrosive	Slippery
Litmus Test	Turns blue litmus red	Turns red litmus blue
pH Value	Less than 7	Greater than 7
Examples	Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄)	Sodium hydroxide (NaOH), Ammonia (NH₃)

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

Ans: Ammonia turns red litmus blue, indicating that it is a base.

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

Source: Litmus solution is obtained from lichens.

Use: It is used as an indicator to determine whether a substance is acidic or basic.

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

Distilled water is neutral.

Verification:

To verify, you can use a litmus test. Both red and blue litmus papers will remain unchanged when dipped in distilled water.
Alternatively, a pH meter can be used to measure the pH, which should be around 7 for neutral water.

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

Neutralisation is the chemical reaction between an acid and a base to form a salt and water.

Example:

When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH): HCl+NaOH→NaCl+H2O

Here, HCl is the acid, NaOH is the base, NaCl is the salt formed, and H₂O is water.

6. True or False Statements

(i) Nitric acid turns red litmus blue. (F)

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

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

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

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

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?

Dorji can use a litmus test to identify the nature of the drinks:

For the acidic drink, red litmus will remain red, and blue litmus will turn red.
For the basic drink, red litmus will turn blue.
For the neutral drink, neither red nor blue litmus paper will change color.

8. Explanation of Various Situations

(a) Antacid Tablet for Acidity: An antacid tablet contains a base which neutralizes the excess stomach acid (HCl) providing relief from acidity.

(b) Calamine Solution for Ant Bites: Calamine contains zinc carbonate or zinc oxide, which are mild bases that neutralize the formic acid injected by the ant bite, relieving the irritation and itching.

(c) Neutralising Factory Waste: Factory waste often contains acids or bases. Before disposing of it into water bodies, it is neutralized to prevent harm to aquatic life and the environment by bringing the pH to a neutral level.

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.

Turmeric indicator turns red in a basic solution but remains yellow in neutral and acidic solutions.

Hydrochloric acid: Turmeric will remain yellow.
Sodium hydroxide: Turmeric will turn red.
Sugar solution: Turmeric will remain yellow.

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

If blue litmus paper remains blue when dipped in a solution, the solution is either neutral or basic. Since blue litmus does not change in basic or neutral solutions, it indicates that the solution is not acidic.

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.

(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

Correct statements: (iv) only d – Change of colour in an acid and a base depends on the type of the indicator.

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