Samacheer Kalvi 9th Term II Science Book Back Question and Answers – Unit 6:

Samacheer Kalvi 9th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 9 Science Book Term 2 Unit 6 – Acids, Bases, and Salts Answers/Solutions are provided on this page. 9th Std Science Book is of Term 1st, 2nd, 3rd, and consists of 9 Units in each Term. All 9 Units of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

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Samacheer Kalvi 9th Science Book Back Unit 6 Term 2 Solutions Guide PDF:

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Term – 2

Unit – 6

Acids, Bases and Salts

I.   Choose the correct answer:

1. Zn + 2HCI à ZnCI₂ +                     
(H₂, O₂, CO₂)

2. Apple contains malic Orange contains _____
(citric acid, ascorbic acid)

3. Acids in plants and animals are organic acids where as acids in rocks and minerals are                     
(Inorganic acids, weak acids)

4. Acids turn blue litmus paper to                    
(Green, Red, Orange)

5. Since metal carbonate and metal bicarbonate are basic they react with acids to give slat and water with the liberation of               
(NO₂, SO₂, CO₂)

6. P^H value of human blood is
(7.0, 4, 7.6)

7. The nature of the tooth paste commonly used is in nature.
(acidic, basic, neutral)

8. You are given pure water to test the p^H value using p^H It shows color.
(white, black, green)

9. The hydrated salt of copper sulphate has
(Red, White, Blue)

II. Short Questions & Answers

1.  Name any two metals which do not react with sodium hydroxide.

Copper and silver (Cu, Ag)

2.  Write any four uses of acids

• Sulphuric acid is called king of chemicals because it is used in the preparation of many other It is used in car batteries also.
• Hydrochloric acid is used as a cleaning agent in
• Citric acid is used in the preparation of effervescent salts and as a good
• Nitric acid is used in the manufacture of fertilizers, dyes, paints and

3.  Give the significance of P^H of soil in agriculture.
In agriculture, the pH of soil is very important. Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil.

4.  When does the acid rain occur?
If the atmospheric air is polluted with oxide gases of sulphur and nitrogen, they get dissolved in rainwater and make its pH less than 7. Thus, ifthe pH of rain water is less than 7, then it is called acid rain.

5.  What are the uses of Plaster of Paris?
Plaster of Paris (Calcium Sulphate Hemihydrate – CaSO₄ .1/2 H₂O)
i) It is used for plastering bones
ii) It is used for preparing moulds for

6. Two acids ‘A’ and ‘B’ are given. Acid A gives one hydrogen ion per molecule of the acid in solution. Acid B gives two hydrogen ions per molecule of the acid in solution.

i)   Find out the acid A and acid B
a) HCI b) H₂SO₄

ii)   Which acid is called the king of chemicals?
Sulphuric acid

7.  Define aquaregia.
The term aquaregia is a Latin phrase meaning ‘King of water’. The name reflects the ability of aquaregia to dissolve the noble metals such as gold, platinum and palladium.

8.  Correct he mistakes

a) Washing soda is used for making cakes and bread soft,
Baking soda is used for making cakes and bread soft, spongy.

b) Calcium sulphate hemihydrates is used in textile
Calcium oxychloride (Bleaching powder) is used in textile industry.

9. Find the odd one
Lemon juice, Tomato juice, House hold ammonia, Coffee
Odd one: Household ammonia

10.  What is neutralization reaction? Give an example.
When an acid reacts with a base it forms salt and water. This is called neutralization reaction. NaOH + HCI à NaCI + H₂O

III. Answer in detail

1. Why does distilled water not conduct electricity whereas rain water does?
Pure water has no ions and it is a non conductor of electricity. Distilled water is pure. So it does not conduct electricity. Rain water has salt and impurities dissolved in it.   the presence of ions in rain water with dissolved salts enables it to conduct electricity.

2. Plaster of Paris should be stored in a moisture proof container, Why?
Calcium Sulphate Hemihydrate is called Plaster of Paris. As it is hygroscopic in nature it absorbs moisture. So plaster of Paris should be stored in a moisture proof container.

3. Write any four used of bases.

i) Sodium hydroxide is used in the manufacture of
ii) Calcium hydroxide is used in white washing of
iii) Magnesium hydroxide is used as a medicine for stomach
iv) Ammonium hydroxide is used to remove grease stains from

4. The solutions A,B,C,D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Among these which solution is

i) neutral – 7
ii) strongly alkaline – 11
iii) Strongly acidic – 1
iv) weakly acidic – 4
v) weakly alkaline – 9

5. Write any five used of salts.

1. Common salt (NaCI)
It is sued in our daily food and it is used as a preservative.

2. Washing soda (Sodium Carbonate)
It is used in softening hard water.

3. Baking Soda ( Sodium Bicarbonate – NaHCO₃)
It is used in making of baking powder which is a mixture of baking soda and tartaric acid.

4. Bleaching powder ( Calcium Oxychloride – CaOCI₂)
It is used as disinfectant.

5. Plaster of Paris (Calcium Sulphate Hemihydrate – CaSO₄ -½ H2O)
It is used for plastering

6. Sulphuric acid is called king of chemicals. Why is it called so?
Sulphuric acid is called King of Chemicals because it is used in the preparation of many other compounds. It is used in car batteries also.

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