NCERT Solutions for Class 12 Chemistry Chapter 16 - Chemistry In Everyday Life

NCERT Exercise

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

Ans: The classification of drugs and the reasons for classification are as follows: 

1. On the Basis of Pharmacological Effect: 

This classification provides doctors the whole range of drugs available for the treatment of a particular type of disease. Therefore, such a classification is very useful to doctors. 

2. On the Basis of Drug Action: 

This classification is based on the action of a drug on a particular biochemical process. Thus, this classification is advantageous in identifying the use of a particular drug. 

3. On the Basis of Chemical Structure: 

This classification provides the range of drugs sharing common structural features and often having similar pharmacological activity. 

4. On the Basis of 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: In medicinal chemistry, drug targets refer to the key molecules involved in certain metabolic pathways that result in specific diseases. Carbohydrates, proteins, lipids, and nucleic acids are examples of drug targets. Drugs are chemical agents designed to inhibit these target molecules by binding with the active sites of the key molecules. 

3. Name the macromolecules that are chosen as drug targets. 

Ans: The macromolecules 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 can cause harmful effects when taken in higher doses than recommended. As a result, the intake of medicines may be poisonous and can cause abnormalities. Hence, medicines should not be taken without consulting the doctors. 

5. Define the term chemotherapy. 

Ans: The use of chemicals for therapeutic effect is called chemotherapy. For example: the use of chemicals in the diagnosis, prevention, and treatment of diseases like cancer.

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

Ans: Either of the following forces can be involved in holding drugs to the active sites of enzymes. 

1. Ionic bonding

2. Hydrogen bonding

3. Dipole – dipole interaction

4. van der Waals forces

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

Ans: Specific drugs affect only particular receptors. Antacids and anti-allergic drugs work on different receptors. This is the reason why antacids cure acidity caused by histamine and anti-allergic drugs cure allergy due to histamines and they do not interfere with each other’s functions, but interfere with the functions of histamines. 

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

Ans: Antidepressant drugs are needed to cure the effect of depression. These drugs inhibit Enzymes catalysing the degradation of the neurotransmitter, noradrenaline. As a result, the important neurotransmitter is slowly metabolised that results in activation of its receptor for longer periods of time.

Two antidepressant drugs are: 

1. Iproniazid 

2. Phenelzine 

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

Ans: Antibiotics that prove to be effective against a wide range of gram-positive and gram-negative bacteria are known as broad spectrum antibiotics. For example, Chloramphenicol is a broad spectrum antibiotic.

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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 are synthetically modified from penicillin that are also broad spectrum antibiotics. 

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

Ans: Antiseptics and disinfectants are effective against microorganisms. They differ in the function that antiseptics are applied to the living tissues such as wounds, cuts, ulcers, and diseased skin surfaces, while disinfectants are useful upon inanimate objects such as cleaning floors, drainage system, instruments, etc. Disinfectants are harmful to the living tissues. 

Iodine is an example of a strong antiseptic. Tincture of iodine (2 - 3 percent of solution of iodine in alcohol - water mixture) is applied to wounds. one percent solution of phenol is used as a disinfectant.

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 they are not effective in treating the actual cause of excess of acid in the stomach. Cimetidine and ranitidine are better antacids as they work on the root cause of acidity. These drugs prevent the interaction of histamine with the receptors present in the stomach walls that results in the 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 percent solution of phenol is used as an antiseptic, while one percent 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.

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

Ans: Tincture of iodine is a 2 − 3 percent solution of iodine in alcohol and water mixture. It works as an antiseptic for wounds and cuts. 

15. What are food preservatives? 

Ans: Food preservatives are chemicals that are used to prevent food from spoilage due to microbial growth. Table salt, sugar, vegetable oil, sodium benzoate$\left( {{C}_{6}}{{H}_{5}}COONa \right)$ , 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 becomes unstable at higher temperatures that are suitable for cooking. Thus, its use is limited to cold foods and drinks due to their low temperature. 

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

Ans: Artificial sweetening agents are chemicals that are used to impart sweet flavor to the food items. However, unlike natural sweeteners, they do not add calories to our body and do not harm the human body. Some commonly used 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, alitame, and aspartame can be used in preparing sweets for diabetic patients. 

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

Ans: Alitame consists of a high potency of sweetening. 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: Soaps have a cleansing action in soft water. But, they are not effective in hard water. In contrast, synthetic detergents work both in soft water and hard water. Therefore, synthetic detergents are better than soaps. 

21. Explain the following terms with suitable examples.

1. Cationic Detergent 

Cationic detergents are quaternary ammonium salts of chlorides, bromides or acetates. 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 

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2. Anionic Detergents 

Anionic detergents are of two types: 

1. Sodium Alkyl Sulphates: These anionic detergents are sodium salts of long chain alcohols. They are prepared by first treating alcohols with concentrated sulphuric acid and then with sodium hydroxide. Examples of these detergents consist of sodium lauryl sulphate

\[~\left( {{C}_{11}}{{H}_{23}}C{{H}_{2}}OS{{O}_{3}}^{-}N{{a}^{+}}\text{ } \right)\text{and sodium stearylsulphate}~\left( {{C}_{17}}{{H}_{35}}C{{H}_{2}}OS{{O}_{3}}^{-}N{{a}^{+}}\text{ } \right)\]

2. Sodium Alkylbenzene Sulphonates: These anionic detergents are sodium salts of long chain alkyl benzene sulphonic acids. They are prepared by Friedel-Crafts alkylation reaction of benzene with long chain alkyl halides or alkenes. The obtained product is first treated with concentrated sulphuric acid and then with sodium hydroxide. For example, Sodium 4-(1-dodecyl) benzenesulfonate (SDS).

3.  Non-Ionic Detergents 

Molecules of these detergents do not contain any ions. These detergents are esters of alcohols having large molecular mass. They are obtained by reacting polyethylene glycol and stearic acid. The reaction is as follows:

$\underset{Stearic\,acid}{\mathop{C{{H}_{3}}{{(C{{H}_{2}})}_{16}}COOH}}\,+\underset{polyethylene\,glycol}{\mathop{HO{{(C{{H}_{2}}C{{H}_{2}}O)}_{n}}C{{H}_{2}}C{{H}_{2}}OH}}\, \\ $

$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\downarrow -{{H}_{2}}O \\ $

$C{{H}_{3}}{{(C{{H}_{2}})}_{16}}COO{{(C{{H}_{2}}C{{H}_{2}}O)}_{n}}C{{H}_{2}}C{{H}_{2}}OH \\ $

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

Ans: Detergents that can be easily degraded by bacteria are called biodegradable detergents. Such detergents have straight hydrocarbon chains. For example: sodium lauryl sulphate.

 Detergents that cannot be degraded by bacteria are called non-biodegradable detergents. Such detergents have highly-branched hydrocarbon chains due to which they are not degraded easily. For example: sodium -4- (1, 3, 5, 7- tetra methyl octyl) benzene sulphonate.

24. Why do soaps not work in hard water? 

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

\[\underset{Soap}{\mathop{2{{C}_{17}}{{H}_{35}}COONa}}\,+CaC{{l}_{2}}\to 2NaCl+\underset{\begin{smallmatrix} \,Insoluble\,calcium\,stearate \\ (soap)\end{smallmatrix}}{\mathop{{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Ca}}\] 

 Therefore, soaps do not work in hard water.

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

Ans: Soaps get precipitated and form an insoluble scum 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.

26. Explain the cleansing action of soaps 

Ans: Soap consists of two parts, one hydrophobic or water repelling and the other hydrophilic or water dissolving. 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.

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27. 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 scum that is of no further use for cleaning. However, when synthetic detergents are dissolved in water containing calcium ions, these ions form soluble salts that act as cleansing agents. 

28. Label the hydrophilic and hydrophobic parts in the following compounds. 

(i)$\text{C}{{\text{H}}_{\text{3}}}{{\text{(C}{{\text{H}}_{\text{2}}}\text{)}}_{\text{10}}}\text{C}{{\text{H}}_{\text{2}}}\text{OS}{{\text{O}}_{\text{3}}}\overset{\text{-}}{\mathop{{}}}\,\overset{\text{+}}{\mathop{\text{Na}}}\,$ 

Ans:

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(ii) $\text{C}{{\text{H}}_{\text{3}}}{{\text{(C}{{\text{H}}_{\text{2}}}\text{)}}_{\text{15}}}\overset{\text{+}}{\mathop{\text{N}}}\,{{\text{(C}{{\text{H}}_{\text{3}}}\text{)}}_{\text{3}}}\overset{\text{-}}{\mathop{\text{Br}}}\,$

Ans: (image will be uploaded soon)

(iii) $\text{C}{{\text{H}}_{\text{3}}}{{\text{(C}{{\text{H}}_{\text{2}}}\text{)}}_{\text{16}}}\text{COO(C}{{\text{H}}_{\text{2}}}\text{C}{{\text{H}}_{\text{2}}}\text{O}{{\text{)}}_{\text{n}}}\text{C}{{\text{H}}_{\text{2}}}\text{C}{{\text{H}}_{\text{2}}}\text{OH}$

Ans: (image will be uploaded soon)

Intext Solution 

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: Most drugs when taken in doses higher than recommended may cause harmful effects and sometimes, may even lead to death. Sleeping pills are one such category of drugs that depresses the functioning of the brain and central nervous system to induce sleep. 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 under 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. 

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 increases the blood glucose levels that may prove harmful for them. Therefore, artificial sweetening agents that do not add to the calorie intake of a person are required. Saccharin, aspartame, and alitame are a few examples of commonly used 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. 

1. ${{\text{(}{{\text{C}}_{\text{15}}}{{\text{H}}_{\text{31}}}\text{COO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}}$ Glyceryl palmitate 

Ans: Preparation of soap from Glyceryl palmitate is as follows:

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2. ${{\text{(}{{\text{C}}_{\text{17}}}{{\text{H}}_{\text{33}}}\text{COO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}}$ Glyceryl oleate 

Ans: Preparation of soap from Glyceryl oleate is as follows:

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5. Following types 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. 

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Ans: The hydrophobic part and the hydrophilic part in the given molecule are as follows:

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Functional groups present in the molecule are: 

1. Ether, and 

2. primary alcoholic group.