Lesson 14 Acids, Bases and Salts
In this post, we are discussing Lesson 14 on “Acids, Bases, and Salts.” The post includes multiple-choice questions, book back answers, and detailed answers to various questions related to acids, bases, and salts. The questions cover topics such as acid-base reactions, pH value, uses of acids and bases, tests to identify acids and bases, uses of salts, and more.
Acids, Bases and Salts Book Back Answer
In the first section, labelled “I. Choose the correct answer,” there are several multiple-choice questions related to acids, bases, and salts. Each question is followed by the correct answer represented by “Ans:” in red colour.
I. Choose the correct answer
1. Zn + 2 HCl → ZnCl2 + …↑(H2, O2, CO2)
Ans: H2
2. Apple contains malic acid. Orange contains (citric acid, ascorbic acid)
Ans: ascorbic acid
3. Acids in plants and animals are organic acids. Whereas Acids in rocks and minerals are (Inorganic acids, Weak acids)
Ans: Inorganic acids
4. Acids turn blue litmus paper to (Green, Red, Orange)
Ans: Red
5. Since metal carbonate and metal bicarbonate are basic they react with acids to give salt and water with the liberation of (NO2, SO2, CO2)
Ans: CO2
6. pH value of human blood is (7.0, 7.4, 7.6)
Ans: 7.4
7. The nature of the tooth paste commonly used is in nature (acidic, basic, neutral)
Ans: basic
8. You are given pure water to test the pH value using pH paper. It shows colour (White, black, green)
Ans: green
9. The hydrated salt of copper sulphate has colour (Red, White, Blue)
Ans: Blue
II. Answer in brief
1. Classify the various types of Acids based on their sources.
The acids are classified based on their sources and organic and inorganics acids.
- Organic acids – acids present in plants and animals
- Inorganics acids – acids prepared from rocks and minerals
2. Write any four uses of acids.
- Hydrochloric acid is used as a cleansing agent in toilets.
- Citric acid is used in the preparation of effervescent salts and as a food preservative.
- Nitric acid is used in the manufacture of fertilizers, dyes, paints and drugs.
- Carbonic acid is used in aerated drinks
- Tartaric acid is a constituent of baking powder.
3. Give the significance of the pH of soil in agriculture.
Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil.
4. What are various uses of Aquaregia
- It is used chief to dissolve metals such as gold and platinum
- It is used for cleaning and refining gold
5. What are the uses of Plaster of Paris?
- It is used for plastering bones
- It is used for making casts for statues
6. Two acids ‘A’ and ‘B’ are given. Acid A gives one hydrogen ion per molecule of the acid in the solution. Acid B gives two hydrogen ions per molecule of the acid in the solution.
(i) Find out the acid A and acid B.
A= HCl (Hydrochloric acid)
B= H2SO2(Sulphuric acid)
(ii) Which acid is called the King of Chemicals?
H2SO2(Sulphuric acid)
7. Define Aquaregia
Aquilegia is a mixture of hydrochloric acid and nitric acid prepared optimally in a molar ratio of 3:1.
8. Correct the mistakes:
a) Washing soda is used for making cakes and bread soft, spongy
Ans: Baking soda is used for making cakes and bread soft, and spongy.
b) Calcium sulphate hemihydrate is used in the textile industry.
Ans: Calcium oxychloride is used in the textile industry.
9. What is the neutralization reaction? Give an example.
Acids react with bases to give salt and water is called a neutralization reaction.
Eg: HCl + NaOH → NaCl + H2O
10. Name any two metals which do not react with sodium hydroxide.
Ag – silver, Cu – Copper
11. When does acid rain occur?
Acid rain is caused by a chemical reaction that beings when compounds like sulphur dioxide and nitrogen oxides are released in to the air. These substances can rise very high into the atmoshere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.
12. Find the Odd one out: Lemon juice, Tomato juice, House hold ammonia, Coffee
Ans: House hold ammonia
III. Answer in Detail
1. Differentiate hydrate and anhydrous salts with examples.
| hydrate | Anhydrous |
| 1. Hydrans is a term used to describe a substance that contains water as an element | Anhydrous is the term used to describe a material that does not contain water as a component. |
| 2. Made up of water molecules | Made up not water molecules |
| 3. These are known as hydrates | These are known as anhydrates |
| 4. Hydroscopic compounds can absorb water from the air to form hydrous compounds | 5. Anhydrous compounds tend to absorb water from air |
| 5. Example: CuSO4 5H2O | Example: NaCl |
2. Give the tests to identify Acids and Bases
a) Test with a litmus paper
An acid turns blue litmus paper into Red. A base turns red litmus paper into Blue.
b) Test with an indicator Phenolphthalein
In an acid medium, phenolphthalein is colourless. In a basic medium, phenolphthalein is pink in colour.
c) Test with an indicator Methyl orange
In acid medium, methyl orange is pink in colour. In basic medium, methyl orange is yellow in colour.
3. Write any four uses of bases.
- Sodium hydroxide is used in the manufacture of soap.
- Calcium hydroxide is used in white washing of building.
- Magnesium hydroxide is used as a medicine for stomach disorder.
- Ammonium hydroxide is used to remove grease stains from cloths.
4. Write any five uses of salts.
Common Salt (NaCl)
It is used in our daily food and used as a preservative.
Washing Soda (Sodium Carbonate)
- It is used in softening hard water.
- It is used in glass, soap and paper industries.
Baking Soda (Sodium bicarbonate -NaHCO3)
- It is used in making of baking powder which is a mixture of baking soda and tartaric acid.
- It is used in soda-acid fire extinguishers.
- Baking powder is used to make cakes and bread, soft and spongy.
- It neutralizes excess acid in the stomach and provides relief.
Bleaching powder (Calcium Oxychloride – CaOCl2)
- It is used as disinfectant.
- It is used in textile industry for bleaching cotton and linen.
Plaster of Paris (Calcium Sulphate Hemihydrate – CaSO4.½ H2O)
- It is used for plastering bones
- It is used for making casts for statues.
5. 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.
- Sulphuric acid is familiar to use as the electrolyte in the lead acidbatteries in automobiles.
- H2SO4 is called king of chemicals because of its high reactivity and corrosive nature.
- It is directly or indirectly used in preparation of most fertilizer and also it can melt large number of metels.
- Sulphuric acid is used in petroleum refining to make high-Octane petrol,which burn efficiency.
- These cleaned up rolls are used to make cars,trucks,as well as household appliances.
- Lost of sulphuric acid used to clean up rust from steel rolls.
6. Why does distilled water not conduct electricity whereas rain water does?
- Distilled water is neutralized.
- No ions in it.
- Ions required to conduct electricity.
- Salts are removed during the
- distillation process.
- Because ions pollutants and salts present in the rain water andso conduct electricity.
7. Plaster of Paris should be stored in a moisture proof container. why?
The plaster of paris should be stored in a moisture-proof container as it absorbs water from moisture and turn into hard substance (Gypsum) as shown in following chemical equaation.
CaSO2.1/2H2O + 3/2 H2O ——–> CaSO4.2H2O
(plastter of paris) (Gypsum)
8. 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
neutral (D solution pH=7)
(ii) strongly alkaline
strongly alkaline (C solution pH=11)
(iii) strongly acidic
strongly acidic (B solution pH=1)
(iv) weakly acidic
weakly acidic (A solution pH=4)
(v) weakly alkaline
weakly alkaline (E solution pH=9)