Chapter 2 – Acids Bases and Salts

Chapter 2 – Acids Bases and Salts Basic Science (2023) Solutions is provided here with simple step-by-step explanations. These solutions for microorganisms are extremely popular among class 8 students for science microorganisms solutions come in handy for quickly completing your homework and preparing for exams.

Book Name	: Basic Science
Subject	: Science
Class	: 7
Publisher	: Bharti Bhawan
Chapter Name	: Acids Bases and Salts

Page No 17:

A. Answer the following in not more than 20 words

Question 1 :

Classify the following substances into acidic and basic substances

Tomato juice, soap solution, toothpaste, lemon juices, vinegar

Answer :

Acidic substances – Tomato juice, lemon juices, vinegar

Basic substance – Toothpaste, soap solution

Question 2 :

Name three mineral acids and give their formulae.

Answer :

• Hydrochloric acid HCl.
• Nitric acid HNO.
• Phosphoric acid H3PO

Question 3 :

Define acids

Answer :

Acids are substances that are sour in taste and they turn blue litmus to red.

Examples: Hydrochloric acid, HCl, and sulphuric acid, H2SO4.

Question 4 :

Define bases

Answer :

Bases are substances that are bitter in taste and they turn red litmus to blue.

Examples: Al₂O₃, Al(OH)₃, CaO, etc.

Question 5 :

What are soluble bases called? Give two examples.

Answer :

Soluble bases are the unique base that dissolves in water without any chemical reaction.

Examples: Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH) etc.

Question 6 :

Define neutral substances.

Answer :

The substances which do not show any color change with litmus paper are called neutral substances.

For example, salt, and ammonium chloride.

Page No 17:

B. Answer the following in not more than 40 words

Question 1 :

Name an acidic gas that is discharged into the atmosphere on the burning of fuels like coal and natural gas. How is this gas formed?

Answer :

The acidic gas formed on the burning of coal is Carbon-di-oxide. It is formed when fuel containing carbon is burned in oxygen, according to the following reaction:

C (s) + O2 (g) → CO2 (g)

Question 2 :

What are the general properties of basic substances?

Answer :

Some of the properties of bases are listed below:

1. Most of the bases are metal hydroxides.
2. They are bitter in taste.
3. They are soapy in touch.
4. They turn red litmus blue.

Page No 17:

C. Answer the following in not more than 100 words

Question 1 :

Write the properties of an acid.

Answer :

Some of the properties of acid are listed below

• Acids have a sour taste.
• Acids change the color of certain acid-base indicates.
• Acids react with active metals to yield hydrogen gas.

Question 2 :

Describe an activity to show the effect of an acid on carbonates and hydrogen carbonates.

Answer :

Take a small amount of metal carbonate (Zinc Carbonate) in Test tube A and metal bicarbonate (Zinc hydrogen carbonate) in test tube B. Pour a few drops of Sulphuric acid into both Test Tubes. You will notice the evolution of a colorless gas.

Balanced equation :

(i) Na₂CO₃ + H₂SO₄ = Na₂SO₄ + CO₂↑ + H₂O

(ii) NaHCO₃ + H₂SO₄ = NaHSO₄ + CO₂↑ + H₂O

Question 3 :

What is acid rain? How it is formed? Mention three bad effects of acid rain.

Answer :

Sulphur dioxide and nitrogen oxides dissolve in rain water and form acids. Such rain is called acid rain.

The three bad effects of acid rain are

• affects the monuments like the Taj Mahal.
• spoils the growth of plants.
• causes irritation of the eyes in human beings.

Question 4 :

Write a note on the uses of bases.

Answer :

The two important uses of bases are as follows.

1. Sodium hydroxide is widely used in the manufacture of soaps and detergents.
2. Magnesium hydroxide is used as an antacid, which gives relief from excess acidity in the stomach.

Page No 17:

D. Complete the following

Question 1 :

The sour things we eat contain ______

Answer :

The sour things we eat contain acids.

Question 2 :

Ammonium hydroxide is an ______

Answer :

Ammonium hydroxide is an alkali

Question 3 :

An acid is _______ by a base.

Answer :

An acid is neutralized by a base.

Question 4 :

An antacid generally contains a ______

Answer :

An antacid generally contains a base.

Page No 17:

E. Choose the correct answer

Question 1 :

Acids are formed when
(a) metals combine with oxygen
(b) oxides of nonmetals dissolve in water
(c) metals react with water
(d) bases dissolve in water

Answer :

(b) oxides of nonmetals dissolve in water

Question 2 :

Hydrochloric acid can be neutralised by
(a) nitric acid
(b) sulphuric acid
(c) citric acid
(d) sodium hydroxide

Answer :

(d) sodium hydroxide

Question 3 :

A soap solution is
(a) acidic
(b) alkaline
(c) neutral

Answer :

(b) alkaline

Question 4 :

In a neutralisation reaction, an acid reacts with a base to give
(a) another acid
(b) another base
(c) another acid and another base
(d) a salt and water

Answer :

(d) a salt and water

Page No 18:

F. Match the column A and B

Question 1 :

A	B
(a) Hydrochloric acid	(i) In-storage batteries
(b) Ascorbic acid	(ii) Found in yogurt
(c) Sulphuric acid	(iii) In making vinegar
(d) Lactic acid	(iv) As a bathroom acid
(e) Acetic acid	(v) Vitamin C

Answer :

(a) – (iv); (b) – (v); (c) – (i); (d) – (ii); (e) – (iii)

Question 2 :

A	B
(a) Sodium Iodate	(i) A food preservative
(b) Calcium sulphate	(ii) Used as a fertilizer
(c) Bleaching powder	(iii) Present in plaster of Paris
(d) Ammonium sulfate	(iv) A disinfectant
(e) Sodium benzoate	(v) A supplement to common salt

Answer :

(a) – (v); (b) – (iii); (c) – (iv); (d) – (ii); (e) – (i)

Page No 18: