NDA Chemistry · Free notes
Chemistry in Everyday Life — NDA Chemistry
Chemistry in Everyday Life is a small, pure named-fact recall chapter — about ten PYQs across 2017–2026, almost every one a 'which chemical / which medicine / which gas' single-fact question. There is nothing to derive; the marks go to whoever has memorised the name↔use pairs. The chapter teaches in two movements: (1) Common chemicals and their uses — the household and industrial substances the bank names by use: washing soda, plaster of Paris, potassium permanganate, silver salts in photography, clean fuels and biogas, and the diver's breathing gas; (2) Medicines and health chemistry — the drug classes (antacid, analgesic, antibiotic, antiseptic versus disinfectant), the calcium compound in tooth enamel, and the radioisotope used to treat cancer. Most concepts are reference tables: learn the table, win the marks. The classic traps are antiseptic-versus-disinfectant and analgesic-versus-antipyretic — same-sounding classes, different jobs.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Common Chemicals and Their Uses
7 PYQsThe household and industrial substances the NDA names by their use — washing soda, plaster of Paris, potassium permanganate, silver salts in photography, clean fuels, biogas, and the gas divers breathe.
Medicines and Health Chemistry
3 PYQsThe drug classes the NDA names by their job — antacid, analgesic, antibiotic, antiseptic versus disinfectant — plus the calcium compound in tooth enamel and the radioisotope used to treat cancer.
Formula & revision sheet
0 formulas · 6 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 6 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (3)
Household chemicals by use4 rows
| Substance | Formula | Common use |
|---|---|---|
| Washing soda | Na₂CO₃·10H₂O | Cleaning; softening hard waterQ Washing soda = sodium carbonate (Na₂CO₃). Baking soda is sodium bicarbonate (NaHCO₃) — different substance. |
| Plaster of Paris | CaSO₄·½H₂O | Casts, moulds, blackboard chalkQ Plaster of Paris is CaSO₄·½H₂O (hemihydrate) — NOT CaSO₄·2H₂O. CaSO₄·2H₂O is gypsum. This wrong formula is the bank's favourite 'NOT correct' statement. |
| Potassium permanganate | KMnO₄ | Purifies drinking water (oxidizing agent)Q KMnO₄ purifies water because it is an oxidizing agent — it oxidises (destroys) organic impurities and microbes. |
| Silver bromide | AgBr | Black-and-white photography (light-sensitive)Q Silver halides (AgBr, AgCl) darken in light — used in photographic film. Not a silver oxide or nitrate here. |
Clean fuels and biogas3 rows
| Fuel | Main component | Note |
|---|---|---|
| Clean fuel / LPG | Propane (C₃H₈) with butane | Burns cleanly, little sootQ Propane is the clean-fuel answer; it is a key component of LPG. |
| Biogas (gobar gas) | Methane (CH₄) | From anaerobic decay of organic wasteQ Biogas is MAINLY methane (≈ 50–70%), with carbon dioxide as the next gas. The major constituent is methane. |
| CNG (vehicle fuel) | Methane (CH₄) | Compressed natural gas; cleaner than diesel |
Gas mixtures for breathing2 rows
| Use | Gas mixture | Why |
|---|---|---|
| Deep-sea diving | Oxygen + helium (heliox) | Helium avoids nitrogen narcosis; low density eases breathingQ Divers breathe oxygen + HELIUM — not oxygen + nitrogen. Nitrogen at depth causes narcosis. |
| Hospital / medical use | Oxygen (sometimes with helium or CO₂) | Pure oxygen or controlled mixtures for patients |
Watch out for (6)
- Plaster of Paris is CaSO₄·½H₂O, not CaSO₄·2H₂O→ Household chemicals by use
- Washing soda ≠ baking soda→ Household chemicals by use
- KMnO₄ disinfects by oxidising, not by killing on contact→ Household chemicals by use
- Biogas is mainly methane, not carbon dioxide→ Clean fuels and biogas
- LPG and CNG are different gases→ Clean fuels and biogas
- Divers breathe oxygen + helium, not oxygen + nitrogen→ Gas mixtures for breathing
Reference tables (3)
Drug classes by their job6 rows
| Class | Job | Example |
|---|---|---|
| Antacid | Treats indigestion / acidity | Milk of magnesia, NaHCO₃Q Antacid is the answer for indigestion — it neutralises excess stomach acid. |
| Analgesic | Relieves pain | Aspirin, paracetamol |
| Antipyretic | Reduces fever | Paracetamol |
| Antibiotic | Kills bacteria | Penicillin |
| Antiseptic | Kills microbes on living skin/tissue | Dettol, tincture of iodine Antiseptic is for the BODY (cuts, skin). Disinfectant is for SURFACES (floors). Same idea, different place. |
| Disinfectant | Kills microbes on non-living surfaces | Phenol, chlorine, bleach |
Radioisotopes and elements in medicine4 rows
| Isotope | Medical use |
|---|---|
| Cobalt-60 | Radiotherapy for cancer (gamma rays)Q Cobalt-60 is the cancer-treatment isotope the bank asks for ('cobalt therapy'). |
| Iodine-131 | Thyroid diagnosis and treatment |
| Sodium-24 | Tracing blood circulation |
| Phosphorus-32 | Treating certain blood disorders |
Chemistry of the body — bones and teeth2 rows
| Body part | Main chemical |
|---|---|
| Tooth enamel | Calcium phosphate (hydroxyapatite)Q Tooth enamel = calcium phosphate. Not calcium carbonate or calcium chloride. |
| Bones | Calcium phosphate (with some carbonate) |
Watch out for (5)
- Antiseptic (skin) versus disinfectant (surfaces)→ Drug classes by their job
- Analgesic (pain) versus antipyretic (fever)→ Drug classes by their job
- Antacid treats acidity, not infection→ Drug classes by their job
- Cobalt-60 treats cancer; iodine-131 treats the thyroid→ Radioisotopes and elements in medicine
- Tooth enamel is calcium phosphate, not calcium carbonate→ Chemistry of the body — bones and teeth
PYQ weightage by concept
6 concepts · 10 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
6 concepts · 10 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Household chemicals by use | 4 | 40% |
| Clean fuels and biogas | 2 | 20% |
| Gas mixtures for breathing | 1 | 10% |
| Concept | PYQs | Share |
|---|---|---|
| Drug classes by their job | 1 | 10% |
| Radioisotopes and elements in medicine | 1 | 10% |
| Chemistry of the body — bones and teeth | 1 | 10% |
Test yourself on a real paper
Sit a past NDA paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.