Chemistry in Everyday Life (Not for Exams)-Solutions

CBSE Class 12 Chemistry

NCERT Solutions
Chapter - 16
Chemistry In Everyday Life

In-text Question

1. Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to take its doses without consultation with the doctor, Why?

Ans. Sleeping pills contains drugs which may be tranquilizers or antidepressants. Most drugs when taken in doses higher than recommended may cause harmful effects and sometimes, may even lead to death. Hence, a doctor should always be consulted before taking any medicine.

2. With reference to which classification has the statement, 'ranitidine is an antacid" been given?

Ans. The given statement refers to the classification of pharmacological effects of the drug. This is because any drug that is used to counteract the effects of excess acid in the stomach is called an antacid. It is sold in the market under the trade name of Zintac or Aciloc.

3. Why do we require artificial sweetening agents?

Ans. A large number of people are suffering from diseases such as diabetes and obesity. These people cannot take normal sugar i.e., sucrose as it is harmful for them. Therefore, artificial sweetening agents that do not add to the calorie intake of a person are required. These also protect teeth from decaying. Saccharin, aspartame, and alitame are a few examples of artificial sweeteners.

4. Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate. Structural formulae of these compounds are given below.
(i) (C15H31COO)3C3H5 - Glyceryl palmitate
(ii) (C17H33COO)3C3H5 - Glyceryl oleate

Ans. Glyceryl palmitate and glyceryl oleate reacts with strong alkali such as NaOH to form soap. The chemical reactions involved are given below:
(i)
(ii)

5. Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and wetting agents. Label the hydrophilic and hydrophobic parts in the molecule. Identify the functional group (s) present in the molecule.

Ans.
Non-ionic detergents are formed by the combination between higher carboxylic acid and polyethylene glycol. Functional groups present in the molecule are:
(i) Ether, and
(ii) primary alcoholic group

Chapter End Question

1. Why do we need to classify drugs in different ways?

Ans. There are large variety of drugs for different purposes of diagnosis, prevention, relief or cure of disease. These drugs have been classified in different ways on the following basis.

Pharmacological effect: It is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular disease.
Drug action: It is based on the action of a drug on a particular biochemical process. Thus, this classification is important.
Chemical structure: It provides the range of drugs sharing common structural features and often having similar pharmacological activity.
Molecular targets: This classification provides medicinal chemists the drugs having the same mechanism of action on targets. Hence, it is the most useful to medicinal chemists.

2. Explain the term, target molecules or drug targets as used in medicinal chemistry.

Ans. Target molecules or drug targets: Drugs interact with macro molecules such as proteins, carbohydrates, fats and oils and nucleic acid and hence, called drug targets. These macro molecules or drug targets play several roles in the body. Drugs are chemical agents designed to inhibit these target molecules by binding with the active sites of the key molecules.

3. Name the macro molecules that are chosen as drug targets.

Ans. The macro molecules chosen as drug targets are carbohydrates, lipids, proteins, and nucleic acids.

4. Why should not medicines be taken without consulting doctors?

Ans. A medicine can bind to more than one receptor site. Thus, a medicine may be toxic for some receptor sites. Further, in most cases, medicines cause harmful effects when taken in higher doses than recommended. As a result, medicines may be poisonous in such cases. Hence, medicines should not be taken without consulting doctors.

5. Define the term chemotherapy.

Ans. Chemotherapy means the treatment of disease by means of chemicals (drugs) to injure or destroy infectious micro-organism without harming micro-organism or bacteria which the body needs.

6. Which forces are involved in holding the drugs to the active site of enzymes?

Ans. Forces holding drugs to the active sites of enzymes are :

Ionic bonding
Hydrogen bonding
Dipole - dipole interaction
van der Waals force

7. Why antacids and anti allergic drugs interfere with the function of histamines, but why do these not interfere with the function of each other?

Ans. Specific drugs affect particular receptors. Antacids and anti-allergic drugs work on different receptors. This is the reason why antacids and anti-allergic drugs do not interfere with each other's functions, but interfere with the functions of histamines. Secretion of histamine causes allergy and acidity while antacids removes only acidity.

8. Low level of noradrenaline is the cause of depression. What types of drugs are needed to cure this problem? Name two drugs.

Ans. Low level of noradrenaline which acts as a neurotransmitter reduces the signal sending activity to the nerves, and the person suffers from depression. Anti-depressant drugs are needed to counteract the effect of depression. These drugs inhibit enzymes catalysing the degradation of the neurotransmitter, noradrenaline. As a result, the important neurotransmitter is slowly metabolised and then it can activate its receptor for longer periods of time.
Two anti-depressant drugs are:

Iproniazid
Phenelzine

9. What is meant by the term 'broad spectrum antibiotics'? Explain.

Ans. Antibiotics that are effective against a wide range of gram-positive and gram-negative bacteria are known as broad spectrum antibiotics. Chloramphenicol is a broad spectrum antibiotic.

It can be used for the treatment of typhoid, dysentery, acute fever, pneumonia, meningitis, and certain forms of urinary infections. Two other broad spectrum antibiotics are vancomycin and ofloxacin. Ampicillin and amoxicillin -synthetically modified from penicillin - are also broad spectrum antibiotics.

10. How do antiseptics differ from disinfectants? Give one example of each.

Ans. Antiseptics and disinfectants are effective against micro-organisms. However, antiseptics are applied to the living tissues such as wounds, cuts, ulcers, and diseased skin surfaces. For example, dettol and savlon. Iodine is an example of a strong antiseptic. Tincture of iodine (2-3% of solution of iodine in alcohol - water mixture) is applied to wounds. Soframycin and furacin are well known antiseptic creams.
Disinfectants are chemical substance which kill micro-organism or stop their growth and are applied to inanimate objects such as floors, drainage system, instruments, etc. Disinfectants are harmful to the living tissues.e.g. 1% solution of phenol and chlorine (0.2-0.4ppm)

11. Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminium hydroxide?

Ans. Antacids such as sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide work by neutralising the excess hydrochloric acid present in the stomach. But the excess and prolong use of these makes stomach alkaline and triggers the release of more HCl which may cause ulcer.
Cimetidine and ranitidine are better antacids as they control the root cause of acidity. These drugs prevent the interaction of histamine with the receptors present in the stomach walls. Consequently, there is a decrease in the amount of acid released by the stomach. This is why cimetidine and ranitidine are better antacids than sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide.

12. Name a substance which can be used as an antiseptic as well as disinfectant.

Ans. Phenol can be used as an antiseptic as well as a disinfectant. 0.2% solution of phenol is used as an antiseptic, while 1% of its solution is used as a disinfectant.

13. What are the main constituents of dettol?

Ans. The main constituents of dettol are chloroxylenol and α-terpineol.

Chapter End Question

14. What is tincture of iodine? What is its use?

Ans. Tincture of iodine is a 2-3% solution of iodine in alcohol - water mixture. It is applied to wounds as an antiseptic.

15. What are food preservatives?

Ans. Food preservatives are chemicals that prevent food from spoilage due to microbial growth i.e. bacteria,yeast and mould. Table salt, sugar, vegetable oil, sodium benzoate (C6H5COONa), sodium metabisulphite and salts of propanoic acid are some examples of food preservatives.

16. Why is use of aspartame limited to cold foods and drinks?

Ans. Aspartame is a very good sweetener for foods and drinks. But its use is limited because it decomposes at cooking temperature. This is the reason why its use is limited to cold foods and drinks.

17. What are artificial sweetening agents? Give two examples.

Ans. Artificial sweetening agents are chemicals that sweeten food. However, unlike natural sweeteners, they do not add calories to our body. They do not harm the human body. Some artificial sweeteners are aspartame, saccharin, sucralose, and alitame.

18. Name a sweetening agent used in the preparation of sweets for a diabetic patient.

Ans. Artificial sweetening agents such as saccharin, and aspartame can be used in preparing sweets for diabetic patients.

19. What problem arises in using alitame as artificial sweetener?

Ans. Alitame is a high potency artificial sweetener. Its sweetening capacity is more than 2000 times as compared to sucrose. Therefore, It is difficult to control the sweetness of food while using alitame as an artificial sweetener.

20. How are synthetic detergents better than soap?

Ans. Detergents are soapless soaps because they resemble soaps in their cleansing action but they do not contain usual chemical contents of soap. Soaps work in soft water. However, they are not effective in hard water. In contrast, synthetic detergents work both in soft water and hard water as they produce foam. Another reason behind it is that sulphonic acids and their salts in detergents are soluble in hard water but fatty acids and their salts in soap are insoluble in hard water. Therefore, synthetic detergents are better than soaps.

21. Explain the following terms with suitable examples

(i) Cationic detergents
(ii) Anionic detergents and
(iii) Non-ionic detergents

Ans. (i) Cationic detergent: Cationic detergents are quaternary ammonium salts of amines with acetates, chlorides, or bromides as anions. These are called cationic detergents because the cationic part of these detergents contains a long hydrocarbon chain and a positive charge on the N atom. For example: cetyltrimethylammonium bromide

(ii) Anionic detergents are those which have anionic hydrophilic group. Anionic detergents are of two types:

Sodium alkyl sulphates: These detergents are sodium salts of long chain alcohols. They are prepared by first treating these alcohols with concentrated sulphuric acid and then with sodium hydroxide. Examples of these detergents include sodium lauryl sulphate (C11H23CH2OSO3- Na+) and sodium stearyl sulphate (C17H35CH2OSO3- Na+).
Sodium alkyl benzene sulphonates: These detergents are sodium salts of long chain alkyl benzene sulphonic acids. They are prepared by Friedel-Crafts alkylation of benzene with long chain alkyl halides or alkenes. The obtained product is first treated with concentrated sulphuric acid and then with sodium hydroxide. Sodium 4-(1-dodecyl) benzene sulphonate (SDS) is an example of anionic detergents.

(iii) Non-ionic detergents: Molecules of these detergents do not contain any ions. These detergents are esters of alcohols having high molecular mass. They are obtained by reacting polyethylene glycol and stearic acid.

22. What are biodegradable and non-biodegradable detergents? Give one example of each.

Ans. Detergents that can be degraded by bacteria are called biodegradable detergents. Such detergents have straight hydrocarbon chains. For example: sodium lauryl sulphate, sodium dodecyl benzene sulphonate, etc. They do not cause any pollution problems.
Detergents that cannot be degraded by bacteria are called non-biodegradable detergents. Such detergents have highly-branched hydrocarbon chains. For example: sodium 4-(1,3,5,7- tetramethyl octyl) benzene sulphonate. They pollute river, ponds and lake water.

23. Why do soaps not work in hard water?

Ans. Soaps are sodium or potassium salts of long-chain fatty acids. Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum.

This is the reason why soaps do not work in hard water.

24. Can you use soaps and synthetic detergents to check the hardness of water?

Ans. Soaps get precipitated in hard water, but not in soft water. Therefore, soaps can be used for checking the hardness of water. However, synthetic detergents do not get precipitated either in hard water or in soft water. Therefore, synthetic detergents cannot be used for checking the hardness of water.

25. Explain the cleansing action of soaps.

Ans. Soaps and detergents are strong electrolytes and when dissolved in water they furnish ions.
$C_{17} H_{35} C O O N a \to \underset{s t e a r a t e i o n}{C_{17} H_{35} C O O^{-}} + N a^{+}$
Soap molecules form micelles around an oil droplet (dirt) in such a way that the hydrophobic parts of the stearate ions attach themselves to the oil droplet and the hydrophilic parts project outside the oil droplet. Due to the polar nature of the hydrophilic parts, the stearate ions (along with the dirt) are pulled into water, thereby removing the dirt from the cloth.

The micellization is a reversible process, hence, by diluting an associated colloid, it is possible to revert to the original simple solution. The cleansing action of soap is due to micelles. The grease is absorbed into the interior of micelle and get detached from the fabric.

26. If water contains dissolved calcium hydrogen carbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes?

Ans. Synthetic detergents are preferred for cleaning clothes. When soaps are dissolved in water containing calcium ions, these ions form insoluble salts that are of no further use. However, when synthetic detergents are dissolved in water containing calcium ions, these ions form soluble salts that act as cleansing agents.

27. Label the hydrophilic and hydrophobic parts in the following compounds.
(i) ${C H}_{3} {({C H}_{2})}_{10} {C H}_{2} {O S O}_{3}^{-} {N a}^{+}$
(ii) $C H_{3} {(C H_{2})}_{15} \overset{+}{N} {(C H_{3})}_{3} \bar{Br}$
(iii) CH3(CH2)16COO(CH2CH2O)nCH2CH2OH

Ans. The long hydrocarbon part (non-polar) acts as hydrophobic part while polar group acts as hydrophilic part.
(i)
(ii)
(iii)