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

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

Ans. We need to classify drugs in different ways because different drugs are effective against the particular microorganisms responsible for disease. Drugs can be classified in following ways:

(a) Based on pharmacological effect.

(b) Based on action on a particular biochemical process.

(c) Based on chemical structure.

(d) Based on molecular targets.

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

Ans. Drugs interact with macromolecules such as proteins, carbohydrates, lipids and nucleic acids. Hence, there are called drug targets. Drugs possessing some common structural features may have the same mechanism of action on targets.

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

Ans. Proteins, carbohydrates, lipids and nucleic acids are chosen as drug targets.

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

Ans. If doctor’s advice is not take before using medicines, it may create some effects or may cause another ailment. The dosage of medicine is of equal importance which must be consult by a doctor.

5. Define the term chemotherapy.

Ans. Chemotherapy is the term used with the treatment of diseases by using chemicals as medicines.

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

Ans. The following forces are involved in holding the drugs to the active site of enzymes:

(a) Hydrogen bonding

(b) Ionic bonding

(c) Dipole-dipole interactions

(d) Van der Waal’s interactions

7. While antacids and antiallergic drugs interfere with the function of histamines why do these not interfere with the function of each other?

Ans. They do not interfere with the functioning of each other because they work on different receptors in the body. Histamine stimulates the secretion of pepsin and hydrochloric acid in the stomach. The drug cimetidine (antacid) was designed to prevent the interaction of histamine with the receptors present in the stomach wall. This resulted in release of lesser amount of acid. Antacid and antiallergic drugs work on different receptors.

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

Ans. Noradrenaline is a neurotransmitter and plays an important role in mood changes. Its low level leads to depression, so tranquillizers (antidepressant) are needed. Iproniazid and phenylzine are such two drugs.

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

Ans. Antibiotics which kill or inhibit a wide range of harmful or disease causing bacteria are called broad spectrum antibiotics.

Example: Ampicillin and Amoxycillin.

10. Discuss the effect of pressure and temperature on the adsorption of gases on solids.

Ans. Many times, the some substance can act as an antiseptic as well as disinfectant by changing the concentration by the solution used. For example, 90.2 per cent solution is a disinfectant chlorine is used in India for making water fit for drinking at a concentration of 0.2 to 0.4 ppm. Low concentration of sulphur dioxide is used for sterilizing squashes for preservation. A few points of distinction between antiseptic and disinfectants are listed.

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

Ans. If excess of NaHCO3 or Mg(OH)2 or Al(OH)3 is used, it makes the stomach alkaline and thus triggers the release of even more HCl which may cause ulcer in the stomach. In contrast, cimetidine and ranitidine prevent the interaction of histamine with the receptor cells in the stomach wall and thus release of HCl will be less as histamine stimulates the secretion of acid.

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

Ans. 0.2% solution of phenol acts as antiseptic while 1% solution acts 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. It is dilute solution of iodine (2 – 3%) prepared in ethanol. It is a powerful antiseptics for wounds.

15. What are food preservatives?

Ans. Chemicals which increases the self life of food by preventing the spoilage causing by some microorganism such as bacteria, yeast, moulds etc, are called food preservatives.

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

Ans. This is because it decomposes at baking or cooking temperatures and hence can be used only in cold foods and drinks as an artificial sweetener.

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

Ans. Artificial sweeteners are chemical substances which are sweet in taste but do not add any calories to our body. They are excreted as such through urine. For example, saccharin, aspartame, alitame etc.

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

Ans. Saccharine, aspartame may be used in the preparation of sweets for a diabetic patient.

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

Ans. Alitame is a high potency artificial sweetener. Therefore, it is difficult to control the sweetness of the food to which it is added.

20. How are synthetic detergents better than soaps?

Ans. Advantages of synthetic detergents over soaps are as:

(i) The solubility of synthetic detergents is higher than that of soap.

(ii) Detergents can work with hard water too while soaps cannot.

(iii) Detergents can work even in acidic medium while soaps cannot.

(iv) Detergents are stronger cleansing agents than soaps.

21. Explain the following terms with suitable examples:

(i) Cationic detergents

(ii) Anionic detergents and

(iii) Non-ionic detergents

Ans. (i) Cationic detergents: These are quaternary ammonium salts, chlorides, acetates, bromides etc containing one or more long chain alkyl groups.

For example, cetyltrimethyl ammonium chloride.

(ii) Anionic detergents: These have large anionic part in there molecules. These are of two types:

(a) Sodium alkyl sulphates: For example: sodium lauryl sulphate, C11H23CH2OSO3 Na+.

(b) Sodium alkyl benzene sulphonates: For example: sodium 4-(l-dodecyl) benzene sulphonate (SDS).

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(iii) Neutral or non-ionic detergents: These are esters of high molecular mass alcohols with fatty acids. These can also be obtained by treatment of long chain alcohols by with excess of ethylene oxide in presence of a base. For example, polyethylene glycol stearate,CH3(CH2)16COO (CH2CH2O)11 CH2CH2OH.

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

Ans. Biodegradable detergents: Detergents which are decomposed by microbes are called biodegradable detergents.

Example: Sodium lauryl sulphate.

Non-Biodegradable detergents:

Detergents which are not decomposed by microbes are called non-biodegradable detergents.

Example: Sodium 4–(1, 3, 5, 7, tetramethyloctyl) benzene sulphonate.

23. Why do soaps not work in hard water?

Ans. Soaps are water soluble sodium or potassium salts of higher fatty acids like palmitic acid (C15H31COOH), oleic acid (C17H33COOH) and stearic acid (C17H35COOH). Hard water contains certain calcium and magnesium salts which combine with soaps to form corresponding magnesium compounds. These being insoluble, get separated as curdy white precipitates resulting in wastage of soap.

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

Ans. Soaps can be used to cleck the hardness of water as it forms insoluble precipitate with water. While it is soluble in soft water.

Detergents can not be used to check the hardness of water because it is soluble in both hard as well as soft water.

25. Explain the cleansing action of soaps.

Ans. Cleansing action of soaps: Soaps contain two parts, a large hydrocarbon which is a hydrophobic (water repelling) and a negative charged head, which is hydrophilic (water attracting). In solution water molecules being polar in nature, surround the ions and not the organic part of the molecule. When a soap is dissolved in water the molecules gather together as clusters, called micelles. The tails stick inwards and the head outwards. The hydrocarbon tail attaches itself to oily dirt. When water is agitated, the oily dirt tends to lift off from the dirty surface and dissociates into fragments. The solution now contains small globules of oil surrounded detergent molecules. The negatively charged heads present in water prevent the small globules from coming together and form aggregates. Thus, the oily dirt is removed from the object.

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

Ans. Water containing calcium hydrogen carbonate is hard water. Detergents are preferred over soaps for cleansing clothes in hard water. This is because in case of soaps calcium ions combines with soap to form insoluble calcium salts of soap that separate as scum, and stick to the clothes as gummy mass while the calcium salts are soluble in water in case of detergents.

$$\underset{\text{Sodium steaate (Soap)}}{2\text{C}_{17}\text{HCOO}^{\normalsize-}\text{Na}^{\normalsize+}} + \underset{\text{Calcium hydrogen carbonate (From hard water)}}{\text{Ca(HCO}_{3})_{2}}\xrightarrow{}\underset{\text{Calcium stearate (Insoluble)}}{(\text{C}_{17}\text{H}_{35}\text{COO})_{2}\text{Ca}\downarrow} + 2\text{NaHCO}_{3} $$

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

(i) CH3(CH2)10CH2OSO3 –Na+

(ii) CH3(CH2)15 –N+(CH3)3Br



$$\text{(i)}\space\space\underbrace{\text{CH}_{3}\text{(CH}_{2})\text{CH}_{10}\text{CH}_{2}}_{\text{Hydrophobic part}}\space-\underbrace{\text{OSO}_{3}^{\normalsize-}\text{Na}^{\normalsize+}}_{\text{ Hydrophilic part}}\\\text{(ii)}\space\underbrace{\text{CH}_{3}(\text{CH}_{2})_{15}}_{\text{ Hydrophobic part}} - \underbrace{\text{N}^{\normalsize+}(\text{CH}_{3})_{3}\text{Br}^{\normalsize-}}_{\text{Hydrophilicpart}}\\\text{(iii)}\space\underbrace{\text{CH}_{3}(\text{CH}_{2})_{16}}_{\text{ Hydrophobicpart}}\space-\space\underbrace{\text{COO(CH}_{2}\text{CH}_{2}\text{O})_{n}\text{CH}_{2}\text{CH}_{2}\text{OH}}_{\text{Hydrophilic part}}$$