Class 12 Chemistry Chapter 16 Question Answer | Chemistry in Everyday Life | English Medium

Class 12 Chemistry Chapter 16 Question Answer | Chemistry in Everyday Life | English Medium | ASSEB

Chemistry in Everyday Life

Welcome to HSLC Guru! In this lesson we explore Class 12 Chemistry Chapter 16 — Chemistry in Everyday Life, prepared strictly according to the ASSEB (Assam State School Education Board) syllabus. This chapter shows how chemistry touches our daily life — through the medicines we take, the food we eat, and the cleansing agents we use. You will learn about the classification and therapeutic actions of drugs, the role of chemicals in food, and how soaps and detergents work to clean clothes and skin. Master this chapter for high-scoring board questions.

Summary

Drugs and their Classification: Drugs are chemicals of low molecular mass (~100–500 u) that interact with biological macromolecules and produce a biological response. When this response is therapeutic and useful, the chemical is called a medicine. The use of chemicals for therapeutic purposes is called chemotherapy. Drugs are classified on the basis of (i) pharmacological effect — useful for doctors, e.g., analgesics relieve pain; (ii) drug action — based on action on a particular biochemical process, e.g., antihistamines inhibit histamine; (iii) chemical structure — drugs sharing common structural features fall in one class, e.g., sulpha drugs; and (iv) molecular targets — most useful for medicinal chemists, drugs are grouped according to the biomolecule (enzyme/receptor) they interact with.

Therapeutic Action of Different Classes of Drugs: Antacids neutralise excess acid in the stomach — examples are Mg(OH)₂, Al(OH)₃, NaHCO₃, and modern drugs like ranitidine and cimetidine which inhibit histamine H₂-receptors and reduce HCl secretion. Antihistamines such as cimetidine, brompheniramine, and terfenadine act as antiallergic drugs by competing with histamine for binding sites. Tranquilisers are neurologically active drugs used to treat stress, anxiety, and mental disorders — examples include barbiturates (luminal, seconal — hypnotic), valium (diazepam), meprobamate and equanil. Analgesics reduce pain without causing impairment of consciousness; non-narcotic analgesics include aspirin and paracetamol, while narcotic (opioid) analgesics include morphine and codeine, used in post-operative and terminal care.

Antimicrobials: These destroy or inhibit the growth of micro-organisms. Sulpha drugs (sulphapyridine, sulphadiazine) were the first effective antibacterials. Antibiotics are produced wholly or partly by chemical synthesis and inhibit growth or kill microorganisms — penicillin (the first antibiotic, discovered by Fleming) is narrow-spectrum, while tetracycline, chloramphenicol and ofloxacin are broad-spectrum. Antiseptics (e.g., dettol, savlon, furacin, soframycin, 0.2% phenol, dilute tincture iodine) are applied on living tissues, while disinfectants (1% phenol, chlorine in water, SO₂ in low concentration) are used on inanimate objects like floors and instruments. Antifertility drugs are oral contraceptives containing synthetic hormones — derivatives of estrogen and progesterone such as norethindrone and ethynylestradiol (novestrol) — used to control population.

Chemicals in Food and Cleansing Agents: Artificial sweeteners are non-nutritive sugar substitutes — saccharin (550× sweeter than sucrose, oldest), aspartame (100× sweeter, unstable to heat — used in cold foods), sucralose (600× sweeter, heat-stable, used in cooking), and alitame (2000× sweeter, high potency). Food preservatives prevent spoilage by retarding microbial growth — common ones are sodium benzoate, sorbic acid, salt, sugar, vegetable oil. Soaps are sodium or potassium salts of long-chain fatty acids (stearic, oleic, palmitic) prepared by saponification — alkaline hydrolysis of oils/fats with NaOH or KOH. Types include toilet/bath soaps (better grade, free of alkali), washing soaps (Na soap with rosin/builders), transparent soaps (made by dissolving soap in ethanol), and medicated soaps (containing antiseptics like dettol). Synthetic detergents work in hard and soft water alike: anionic (sodium alkyl benzene sulphonates — used in toothpastes and household powders), cationic (cetyltrimethylammonium bromide — used in hair conditioners), and non-ionic (used in liquid dishwashing detergents). The cleansing action involves the formation of micelles in which the hydrophobic tail traps grease/oil while the hydrophilic head dissolves in water and is washed away.

Question Answer (1 Mark)

Q1. What is a drug?

Answer: A drug is a chemical of low molecular mass (~100–500 u) that interacts with biological macromolecules and produces a biological response.

Q2. Define chemotherapy.

Answer: Chemotherapy is the use of chemicals (drugs/medicines) for therapeutic purposes to treat diseases.

Q3. Name two common antacids.

Answer: Magnesium hydroxide [Mg(OH)₂] and ranitidine.

Q4. What are tranquilisers? Give one example.

Answer: Tranquilisers are neurologically active drugs used to treat stress, mild and severe mental diseases. Example: valium (diazepam).

Q5. Give one example each of a narcotic and a non-narcotic analgesic.

Answer: Narcotic — morphine; Non-narcotic — aspirin (or paracetamol).

Q6. Who discovered penicillin?

Answer: Sir Alexander Fleming discovered penicillin in 1929.

Q7. What is saponification?

Answer: Saponification is the alkaline hydrolysis of oils or fats with NaOH (or KOH) to produce soap and glycerol.

Q8. Name the most common food preservative used in jams and squashes.

Answer: Sodium benzoate.

Q9. Which artificial sweetener is suitable for cooking and baking?

Answer: Sucralose, because it is heat-stable.

Q10. Give one example of a cationic detergent.

Answer: Cetyltrimethylammonium bromide (used in hair conditioners).

Question Answer (2–3 Marks)

Q1. Differentiate between antiseptics and disinfectants with examples.

Answer: Antiseptics are chemicals applied on living tissues like skin, wounds, and ulcers to prevent infection — examples: dettol, savlon, furacin, 0.2% phenol, dilute tincture iodine. Disinfectants are applied on inanimate objects like floors, instruments, and drainage to kill micro-organisms — examples: 1% phenol, chlorine in water, SO₂ in low concentration. The same substance may act as both at different concentrations (e.g., phenol at 0.2% is antiseptic and at 1% is a disinfectant).

Q2. Distinguish between broad-spectrum and narrow-spectrum antibiotics with one example each.

Answer: Broad-spectrum antibiotics are effective against a wide range of Gram-positive and Gram-negative bacteria — example: tetracycline, chloramphenicol. Narrow-spectrum antibiotics are effective only against a particular kind of microorganism — example: penicillin G (effective mainly against Gram-positive bacteria). Broad-spectrum drugs are useful when the causative organism is unknown.

Q3. Explain the cleansing action of soap.

Answer: A soap molecule has a long hydrophobic hydrocarbon tail and a hydrophilic ionic head (–COO⁻Na⁺). When soap is added to water containing greasy clothes, the tails dissolve in oil/grease while the heads remain in water, forming spherical aggregates called micelles. The grease droplet gets trapped inside a micelle, lifted off the cloth, and washed away with water. This emulsification of dirt is the basis of cleansing action.

Q4. Why are synthetic detergents preferred over soaps for washing?

Answer: Soaps form insoluble calcium and magnesium salts (scum) with hard water, wasting soap and leaving deposits. Synthetic detergents are sodium salts of long-chain alkylbenzenesulphonic acids; their Ca²⁺ and Mg²⁺ salts are soluble, so detergents lather and clean effectively in both hard and soft water. They also work in acidic solutions, unlike soaps.

Q5. What are antifertility drugs? Name two.

Answer: Antifertility drugs are synthetic hormones used to control population growth by preventing pregnancy. They are usually mixtures of derivatives of female sex hormones — estrogen and progesterone. Examples: norethindrone (synthetic progesterone) and ethynylestradiol/novestrol (synthetic estrogen).

Q6. Name four common artificial sweeteners and arrange them in order of their sweetness.

Answer: Saccharin (≈550× sucrose), aspartame (≈100× sucrose), sucralose (≈600× sucrose), alitame (≈2000× sucrose). Order of sweetness (low to high): aspartame < saccharin < sucralose < alitame. Aspartame is unstable at cooking temperatures; sucralose is heat-stable and best for cooking.

Question Answer (5–7 Marks)

Q1. Explain the four bases for classification of drugs with examples.

Answer: Drugs are classified on the basis of:

(i) Pharmacological Effect: Based on therapeutic action on the body. Useful for doctors. Example — analgesics relieve pain; antiseptics kill micro-organisms.
(ii) Drug Action: Based on action on a particular biochemical process. Example — antihistamines inhibit the action of histamine, which causes inflammation.
(iii) Chemical Structure: Drugs sharing common structural features are grouped together. Example — sulpha drugs (sulphonamide group), penicillins (β-lactam ring).
(iv) Molecular Targets: Drugs are grouped on the basis of biomolecules (enzymes/receptors) with which they interact. Most useful for medicinal chemists for drug design.

Q2. Discuss the major classes of therapeutic drugs with examples and uses.

Answer:

Antacids: Neutralise stomach acid. Examples — Mg(OH)₂, Al(OH)₃, NaHCO₃, ranitidine (Zantac), cimetidine. Modern antacids inhibit histamine H₂-receptors so that less HCl is released.
Antihistamines: Block histamine receptors and treat allergies. Examples — brompheniramine (Dimetapp), terfenadine (Seldane), cimetidine.
Tranquilisers (Psychotherapeutic): Treat anxiety, stress, sleep disorders. Examples — barbiturates (luminal, seconal — hypnotics), valium (diazepam), meprobamate, equanil.
Analgesics: Reduce pain. Non-narcotic — aspirin, paracetamol, ibuprofen (also anti-inflammatory). Narcotic/opioid — morphine, codeine (used in postoperative and terminal cancer pain).
Antimicrobials: Kill or inhibit microorganisms. Includes sulpha drugs and antibiotics.

Q3. Describe antibiotics. Differentiate between bactericidal and bacteriostatic antibiotics, and broad- and narrow-spectrum antibiotics.

Answer: Antibiotics are chemical substances produced wholly or partly by chemical synthesis, which in low concentration inhibit the growth of or kill micro-organisms by intervening in their metabolic processes. The first antibiotic, penicillin, was discovered by Sir Alexander Fleming.

Bactericidal: Kill bacteria — penicillin, ofloxacin, aminoglycosides.
Bacteriostatic: Inhibit growth of bacteria — erythromycin, tetracycline, chloramphenicol.
Broad-spectrum: Effective against many Gram-positive and Gram-negative bacteria — chloramphenicol, tetracycline, ofloxacin.
Narrow-spectrum: Effective against a single type or limited range — penicillin G (Gram-positive); dihydrostreptomycin (Gram-negative).
Limited-spectrum: Effective against a single organism or disease.

Q4. Describe soaps — types and method of preparation.

Answer: Soaps are sodium or potassium salts of higher fatty acids (stearic, palmitic, oleic). They are prepared by saponification — heating vegetable oil/fat with concentrated NaOH solution. The reaction produces soap and glycerol; common salt is added to precipitate the soap. Reaction:

(C₁₇H₃₅COO)₃C₃H₅ + 3 NaOH → 3 C₁₇H₃₅COONa + C₃H₅(OH)₃

Toilet/Bath Soaps: Better grade — made with KOH; free of alkali; perfume and dye added.
Washing Soaps: Sodium soaps with builders like sodium silicate, sodium carbonate, borax, and rosin.
Transparent Soaps: Made by dissolving the soap in ethanol and evaporating excess solvent.
Medicated Soaps: Contain antiseptics like dettol or chloroxylenol.
Shaving Soaps: Glycerol added to prevent rapid drying; contain rosin.
Soap Chips/Granules/Powders: Made for various household uses; powders also contain abrasives like sand.

Q5. Explain synthetic detergents — types, examples and advantages over soap.

Answer: Synthetic detergents are cleansing agents having all the properties of soap but which actually do not contain any soap. They work even in hard water and acidic solutions. Three types:

Anionic Detergents: Sodium salts of sulphonated long-chain hydrocarbons or alcohols. Example — sodium lauryl sulphate, sodium dodecylbenzenesulphonate (SDS). Used in toothpastes and household washing powders. Anionic part performs cleansing action.
Cationic Detergents: Quaternary ammonium salts of amines with halides/sulphates. Example — cetyltrimethylammonium bromide. Have germicidal properties and are used in hair conditioners but are expensive.
Non-ionic Detergents: Do not contain any ion. Example — esters of stearic acid with polyethylene glycol. Used in liquid dishwashing detergents.

Advantages over soaps: (i) work in hard water and acidic conditions, (ii) better cleansing action, (iii) cheaper. Disadvantage: Detergents with branched hydrocarbon chains are non-biodegradable and cause water pollution.

Multiple Choice Questions (MCQ)

Q1. Which of the following is an example of an antacid?
(a) Aspirin (b) Ranitidine (c) Morphine (d) Penicillin

Answer: (b) Ranitidine.

Q2. Valium and barbiturates belong to the class of:
(a) Antibiotics (b) Antacids (c) Tranquilisers (d) Antiseptics

Answer: (c) Tranquilisers.

Q3. Morphine is a:
(a) Non-narcotic analgesic (b) Narcotic analgesic (c) Antiseptic (d) Antibiotic

Answer: (b) Narcotic analgesic.

Q4. Penicillin was discovered by:
(a) Louis Pasteur (b) Robert Koch (c) Alexander Fleming (d) Edward Jenner

Answer: (c) Alexander Fleming.

Q5. Which of the following is a broad-spectrum antibiotic?
(a) Penicillin G (b) Tetracycline (c) Sulphapyridine (d) Aspirin

Answer: (b) Tetracycline.

Q6. Dettol is an example of:
(a) Disinfectant (b) Antiseptic (c) Antacid (d) Antibiotic

Answer: (b) Antiseptic.

Q7. Which artificial sweetener is about 2000× sweeter than sugar?
(a) Saccharin (b) Aspartame (c) Sucralose (d) Alitame

Answer: (d) Alitame.

Q8. The most widely used food preservative in jams and squashes is:
(a) Salt (b) Sugar (c) Sodium benzoate (d) Vinegar

Answer: (c) Sodium benzoate.

Q9. Soap is a sodium or potassium salt of:
(a) A short-chain carboxylic acid (b) A long-chain fatty acid (c) Sulphuric acid (d) Phosphoric acid

Answer: (b) A long-chain fatty acid.

Q10. Cetyltrimethylammonium bromide is an example of:
(a) Anionic detergent (b) Cationic detergent (c) Non-ionic detergent (d) Soap

Answer: (b) Cationic detergent.

Fill in the Blanks

Q1. Drugs that neutralise excess stomach acid are called __________.

Answer: antacids.

Q2. The alkaline hydrolysis of fats/oils to make soap is called __________.

Answer: saponification.

Q3. __________ are applied on inanimate objects to kill micro-organisms.

Answer: Disinfectants.

Q4. __________ is an artificial sweetener stable at cooking temperature.

Answer: Sucralose.

Q5. Soap molecules form spherical clusters called __________ in water.

Answer: micelles.

True or False

Q1. Aspirin is a narcotic analgesic. — False (it is a non-narcotic analgesic).

Q2. Penicillin is a broad-spectrum antibiotic. — False (it is narrow-spectrum).

Q3. Synthetic detergents work in hard water. — True.

Q4. Aspartame is heat-stable and used in cooking. — False (it decomposes on heating).

Q5. Norethindrone is an antifertility drug. — True.

Glossary

Term	Meaning
Drug	Low-MW chemical (100–500 u) that produces a biological response in the body.
Medicine	Drug used in therapeutic doses for treatment of disease.
Chemotherapy	Use of chemicals for therapeutic purposes.
Antacid	Drug that neutralises excess HCl in the stomach (e.g., Mg(OH)₂, ranitidine).
Antihistamine	Drug that blocks histamine receptors and treats allergy (e.g., cimetidine).
Tranquiliser	Neurologically active drug for stress/anxiety (e.g., valium, barbiturates).
Analgesic	Pain-reliever; non-narcotic (aspirin, paracetamol) or narcotic (morphine).
Antibiotic	Substance that inhibits/kills microorganisms (e.g., penicillin, tetracycline).
Broad-spectrum	Antibiotic effective against many types of bacteria.
Narrow-spectrum	Antibiotic effective against a single type or limited range of bacteria.
Antiseptic	Chemical applied on living tissues to prevent infection (e.g., dettol).
Disinfectant	Chemical applied to inanimate objects to kill germs (e.g., 1% phenol).
Antifertility drug	Synthetic hormone for birth control (e.g., norethindrone).
Artificial sweetener	Non-nutritive sugar substitute (saccharin, aspartame, sucralose, alitame).
Food preservative	Substance that prevents food spoilage (e.g., sodium benzoate).
Saponification	Alkaline hydrolysis of fats/oils to soap and glycerol.
Soap	Sodium/potassium salt of long-chain fatty acid.
Detergent	Synthetic cleansing agent that works in hard water; anionic, cationic, or non-ionic.
Micelle	Spherical aggregate of soap/detergent molecules that traps grease in cleansing.
Hard water	Water containing dissolved Ca²⁺ and Mg²⁺ salts.

Keep practising these notes for HSLC Guru ASSEB Class 12 Chemistry Chapter 16 — Chemistry in Everyday Life. Bookmark this page for revision before your board examination!