📑 Topics on this page (Jump to Topic):
📌 1. Soaps, Detergents & Hard Water
- Soap = sodium/potassium salts of long-chain fatty acids; hard soap — NaOH, soft (bathing/shaving) — KOH. It forms micelles to remove oily dirt.
- In hard water soap forms scum instead of lather; detergents (sulphonate salts) work even in hard water.
- Temporary hardness — Ca/Mg bicarbonates; removed by boiling. Permanent hardness — Ca/Mg chlorides and sulphates; removed by washing soda or ion exchange (permutit/zeolite).
- Water is disinfected with chlorine/bleaching powder, ozone or UV; RO uses a semi-permeable membrane.
📌 2. Fertilisers & Medicines
- Main plant nutrients N-P-K (nitrogen, phosphorus, potassium). Urea has the most nitrogen (~46%). Others: ammonium sulphate, DAP, superphosphate of lime, muriate of potash (KCl).
| Type | Action | Examples |
|---|---|---|
| Analgesic | Relieves pain | Aspirin, paracetamol, morphine (narcotic) |
| Antipyretic | Reduces fever | Paracetamol, aspirin |
| Antibiotic | Kill/stop bacteria (not viruses) | Penicillin (Fleming, 1928), streptomycin (TB), tetracycline |
| Antiseptic | Stop germs on living tissue | Dettol (chloroxylenol + terpineol), tincture of iodine, boric acid |
| Disinfectant | On non-living surfaces | Phenyl, 1% phenol, bleaching powder |
| Tranquilliser | Reduce stress/anxiety | Diazepam (Valium) |
| Antimalarial | Malaria | Quinine (cinchona bark), chloroquine |
| Anaesthetic | Loss of sensation | Chloroform, nitrous oxide (laughing gas), xylocaine |
📌 3. Cement, Glass, Explosives & Food Chemicals
- Portland cement (Joseph Aspdin, 1824): limestone + clay; gypsum added to slow setting. Cement + sand + water = mortar; + gravel = concrete; + steel bars = RCC.
- Ordinary (soda) glass = sand (SiO₂) + soda + lime. Colours: cobalt — blue, chromium — green, manganese — violet, gold — ruby red. Pyrex — borosilicate (laboratory). Glass is a supercooled liquid.
- Explosives: TNT (trinitrotoluene), RDX, nitroglycerine; dynamite — Alfred Nobel. Gunpowder = potassium nitrate + sulphur + charcoal.
- Food preservatives: sodium benzoate, potassium metabisulphite, salt, sugar, vinegar. Artificial sweeteners: saccharin (~300–500× sweeter than sugar), aspartame, sucralose. Flavour enhancer: monosodium glutamate (Ajinomoto).
| Common name | Chemical name / formula |
|---|---|
| Laughing gas | Nitrous oxide N₂O |
| Limestone / marble / chalk | CaCO₃ |
| Quicklime / slaked lime | CaO / Ca(OH)₂ |
| Caustic soda | NaOH |
| Glauber's salt | Na₂SO₄·10H₂O |
| Epsom salt | MgSO₄·7H₂O |
| Green vitriol | FeSO₄·7H₂O |
| Borax | Na₂B₄O₇·10H₂O |
| Silica / sand | SiO₂ |
| Sal ammoniac | Ammonium chloride NH₄Cl |
| Saltpetre | Potassium nitrate KNO₃ |
⚠️ Exam Traps:
- Antibiotics do not work against viruses (cold, flu).
- Gypsum slows down the setting of cement, not speeds it up.
- Urea is a nitrogenous fertiliser, not phosphatic.
📌 4. Practice MCQs
📝 Practice MCQs (prepared by SF Prep — not PYQs)
Q1. Penicillin was discovered by: Practice
Correct answer: (D)
In 1928 from Penicillium mould.
In 1928 from Penicillium mould.
Q2. The chemical name of laughing gas is: Practice
Correct answer: (A)
N₂O — also used as an anaesthetic.
N₂O — also used as an anaesthetic.
Q3. Why is gypsum added to cement? Practice
Correct answer: (C)
Without gypsum, cement would set too fast.
Without gypsum, cement would set too fast.
Q4. Which fertiliser has the highest nitrogen content? Practice
Correct answer: (C)
Urea has ~46% N.
Urea has ~46% N.
Q5. Dynamite was invented by: Practice
Correct answer: (A)
Based on nitroglycerine; the Nobel Prize is named after him.
Based on nitroglycerine; the Nobel Prize is named after him.
Q6. Temporary hardness of water is caused by: Practice
Correct answer: (B)
On boiling they precipitate as carbonates.
On boiling they precipitate as carbonates.
Q7. Why does soap not lather in hard water? Practice
Correct answer: (A)
Detergents do not have this problem.
Detergents do not have this problem.
Q8. Quinine is used to treat: Practice
Correct answer: (D)
Obtained from cinchona bark.
Obtained from cinchona bark.
Q9. Pyrex glass is: Practice
Correct answer: (A)
Heat-resistant — laboratory glassware.
Heat-resistant — laboratory glassware.
Q10. To give glass a blue colour, which is added? Practice
Correct answer: (B)
Chromium — green, manganese — violet.
Chromium — green, manganese — violet.
Q11. Which is used as a food preservative? Practice
Correct answer: (B)
Used in jams, sauces and pickles.
Used in jams, sauces and pickles.
Q12. Antibiotics are NOT effective against: Practice
Correct answer: (D)
Cold and flu are caused by viruses.
Cold and flu are caused by viruses.
Q13. Paracetamol is an: Practice
Correct answer: (C)
It lowers fever and relieves pain.
It lowers fever and relieves pain.
Q14. Gunpowder consists of: Practice
Correct answer: (D)
Black powder — the oldest explosive.
Black powder — the oldest explosive.
Q15. The chemical formula of Epsom salt is: Practice
Correct answer: (C)
Magnesium sulphate; Glauber's salt = Na₂SO₄·10H₂O.
Magnesium sulphate; Glauber's salt = Na₂SO₄·10H₂O.
Q16. Portland cement was invented by: Practice
Correct answer: (D)
1824, England; named for resembling Portland stone.
1824, England; named for resembling Portland stone.
Q17. Saccharin is a: Practice
Correct answer: (B)
Hundreds of times sweeter than sugar, negligible calories.
Hundreds of times sweeter than sugar, negligible calories.
Q18. Dettol is an: Practice
Correct answer: (B)
Chloroxylenol + terpineol; used on living tissue.
Chloroxylenol + terpineol; used on living tissue.
Q19. The chemical name of saltpetre is: Practice
Correct answer: (C)
KNO₃; sal ammoniac = NH₄Cl.
KNO₃; sal ammoniac = NH₄Cl.
Q20. The ion-exchange method for permanent hardness uses: Practice
Correct answer: (A)
Na⁺ ions are exchanged for Ca²⁺/Mg²⁺.
Na⁺ ions are exchanged for Ca²⁺/Mg²⁺.