Strategy
Score 45+ in PART B Chemistry with ~36 hours
15 PART B Chemistry questions × 4 marks − 1.33 per wrong. Three skill strands matched to the bank's actual shape (63% Recall, 42% Rule, 3% Calculate — yes, they add to >100% because some chapters span strands).
- marks out of 60
- 45+
- attempts of 15
- 13
- accuracy needed
- 90%
- total prep time
- ~36 h
The arithmetic of 45+
PART B Chemistry has ~15 questions on the GAT (range 12–18 across the 2017–2026 bank), each worth 4 marks with −1.33 per wrong. Per-paper max ≈ 60 marks. To net 45+ marks:
| Accuracy | Attempts | Correct | Wrong | Net marks | Result |
|---|---|---|---|---|---|
| 75% | 12 | 9 | 3 | ~32 | Miss |
| 90% | 13 | 12 | 1 | ~47 | Target ✓ |
| 93% | 14 | 13 | 1 | ~51 | Stretch ✓ |
Target: attempt 13 of ~15 questions at 90%+ accuracy. Skip the ~2 you’re unsure of. The −1.33 penalty is harsh — and Chemistry’s high recall surface rewards ‘know cold or skip’ more than guessing. If you don’t recognise an allotrope name or a chemical formula within 5 seconds, skip — the −1.33 makes guessing negative-EV at below ~55% confidence.
Recall — Carbon · Matter · Industrial · Metals · Hydrogen · Everyday Life · Practical (144 q · 55%)
Pure fact recall — chemical names, formulas, uses, allotropes, reactivity orderings, lab methods. 144 q at an average of 4% HARD. The highest marks-per-hour strand in the bank, and the strand most students under-invest in (it feels like 'memorisation, not chemistry'). 4 of these 7 chapters carry ZERO HARD across 10 years. Drill the /common-compounds reference page side-by-side with this strand — it covers the highest-leverage memorisation surface.
The approach
- Read /guide/nda-chemistry/common-compounds end-to-end first. That's the ~50 name↔formula↔use pairs the recall strand keeps re-testing. Active-recall it in 4 passes (cover the right column, read the name, write the formula).
- Carbon and Its Compounds is the bank's largest chapter (45 q). Half of it is the Allotropes subtopic (15 q) — diamond vs graphite vs fullerene vs graphene properties + uses. The other half is common compounds + functional groups. Drill the allotropes subtopic separately for fast wins.
- Industrial and Applied Chemistry hides one trap subtopic — Paints and Coatings, 4 q at 75% HARD. Don't skip it, but expect the 'pigment vs drier vs thinner vs anti-skinning' pairs to take longer than the rest of the chapter.
Carbon and Its Compounds
45 questions · 4% hard
45 q · 2 HARD across 10 yrs. Allotropes is the dominant subtopic — memorise the diamond/graphite/fullerene property table cold. Common Compounds is name↔formula↔use recall.
Matter and Its States
30 questions · 3% hard
30 q · 1 HARD across 10 yrs. Five small subtopics, each rule-of-thumb sized. Watch the colloid vs suspension distinction — 1 of 5 q is HARD.
Industrial and Applied Chemistry
28 questions · 11% hard
28 q · 11% HARD (driven by the Paints subtopic — 3 of 4 paint q are HARD). Industrial gases, cement composition, NPK fertiliser percentages, alloy compositions all pure recall.
Metals and Non-Metals
17 questions · 0% hard
17 q · ZERO HARD across 10 yrs. Pure recall. Memorise the reactivity series K-Na-Ca-Mg-Al-Zn-Fe-Cu-Hg-Ag-Au, the four major alloy compositions (brass, bronze, stainless steel, solder), galvanisation = zinc coating.
Hydrogen and Water
11 questions · 9% hard
11 q · 1 HARD across 10 yrs. Permanent (CaSO₄/MgSO₄) vs temporary (Ca(HCO₃)₂) hardness recall + softening methods. Water's anomalous max density at 4 °C.
Chemistry in Everyday Life
10 questions · 0% hard
10 q · ZERO HARD across 10 yrs. Drink/gas/cleaner identification + antacid/analgesic/antibiotic types. The lowest-investment / highest-confidence chapter in the bank.
Practical Chemistry
3 questions · 0% hard
3 q · ZERO HARD across 10 yrs. Lab + food + health applications. Read once in 15 min — the q-yield is low but the marks are essentially free.
Drill
- Practical Applications: Health, Food and Lab MethodsDrill
Rule — Atomic Structure · Acids/Bases/Salts · Reactions · Bonding (109 q · 42%)
Apply specific rules — pH classification (acidic < 7), oxidation-state assignment (sum to zero), periodic-trend prediction (atomic radius decreases across, increases down), redox identification (LEO RGO — Loss of Electrons = Oxidation, Reduction = Gain of e⁻). Four chapters, 109 q at 7% average HARD. The skill is rule-application, not memorisation: the answer follows from the framework, not from a remembered fact.
The approach
- Memorise the 4 master rules first: (1) periodic trends — radius ↓ across, ↑ down; IE ↑ across, ↓ down; EN ↑ across, ↓ down; metallic character opposite. (2) Oxidation-state assignment sequence: H=+1, O=−2, group I=+1, group II=+2, sum to molecule charge. (3) Acid-base type: Arrhenius (water H⁺/OH⁻), Brønsted (H⁺ donor/acceptor), Lewis (e⁻ pair acceptor/donor). (4) Reaction type: A+B→AB combination; AB→A+B decomposition; A+BC→AC+B displacement; AB+CD→AD+CB double-displacement.
- Chemical Reactions (30 q · 10% HARD) is the hottest Rule chapter. Redox subtopic (10 q at 20% HARD) is the marquee — learn LEO RGO + assign oxidation states + identify the species being oxidised (loses e⁻, ox-state ↑) and reduced. Practice with the bank's 5+ pair-property questions.
- Atomic Structure (35 q) gets confused because it mixes pure-recall pieces (atomic models history) with rule-application (periodic trends, electron config). When you drill, separate the subtopics — Periodic Trends + Atomic Number questions reward the rule lens; Atomic Models is mostly recall.
Atomic Structure and Periodic Classification
35 questions · 9% hard
35 q · 9% HARD. Periodic Trends is the biggest subtopic (12 q) — drill the rule once, the rest follows. Watch for 'order of valency' Match-List traps in the HARD pool.
Acids, Bases and Salts
33 questions · 6% hard
33 q · 6% HARD. Five subtopics, each rule-of-thumb sized. Common Acids overlaps with /common-compounds — drill both side-by-side.
Chemical Reactions
30 questions · 10% hard
30 q · 10% HARD — the chapter's hot pool is Redox (10 q at 20% HARD). LEO RGO + oxidation-state assignment cracks 80% of redox questions.
Drill
- Redox: Oxidation, Reduction and Reducing AgentsDrill
- Types of Reactions: Combination, Decomposition, DisplacementDrill
- Specific Reactions: Precipitation, Electrolysis and Daily LifeDrill
- Thermal and Photochemical DecompositionDrill
- Endothermic and Exothermic ReactionsDrill
- Physical vs Chemical ChangesDrill
Chemical Bonding
11 questions · 0% hard
11 q · ZERO HARD across 10 yrs. EN-difference > 1.7 ⟹ ionic; < 1.7 ⟹ covalent. Ox-state from sum-to-charge rule. Pure rule application.
Calculate — Mole Concept and Stoichiometry (9 q · 3%)
The smallest strand, but a distinct skill. 9 q across 10 years, 1 HARD — but the q-yield is reliable (mole/Avogadro questions appear most years, especially NDA-2). Numeric work: mol = mass / molar mass; mol = particles / 6.022×10²³; equivalent weight = molar mass / valency factor; balanced equations → stoichiometric ratios. Don't skip the strand because it's small — it's 1–2 marks per paper, and the formulas are reusable from your Maths prep.
The approach
- Memorise the four core formulas: mol = m/M; mol = N/N_A (where N_A = 6.022×10²³); equiv-weight = molar mass / valency factor; m(g) = mol × molar mass. Practice unit-conversion (g → kg, mL → L) before plugging into formulas.
- Equivalent weight is the recurring tricky form. For acids: equiv-wt = molar mass / basicity (HCl = 36.5 / 1 = 36.5; H₂SO₄ = 98 / 2 = 49; H₃PO₄ = 98 / 3 ≈ 32.7). For bases: / acidity. For salts: / total positive charge. For oxalic acid (C₂H₂O₄·2H₂O): molar mass 126 / valency 2 = 63.
- Stoichiometry questions in NDA Chemistry are usually 'which law of chemical combination is shown' (conservation of mass, definite proportions, multiple proportions). Match the data pattern to the law — don't try to derive from scratch.
Mole Concept and Stoichiometry
9 questions · 11% hard
9 q · 1 HARD across 10 yrs. Small bucket, distinct skill. Drill the equivalent-weight calculation (the recurring tricky form) and the law-identification format.
Test-day attempt order — for PART B Chemistry’s ~15-min slot
Bank Recall marks first (fast, high-confidence), then Rule, then Calculate. Within the GAT 2.5-hour total (150 min for 150 q across English + 5 Part B sections), PART B Chemistry’s share is ~15 min for its ~15 questions — this plan fits inside it.
- 5min
Sweep Recall (Carbon + Matter + Industrial + Metals + Hydrogen + Everyday + Practical)
Scan all ~15 Chemistry questions, mark every Recall-strand item (allotropes, common compounds, separation methods, reactivity series, alloy composition, water hardness, household chemicals). Expect ~8 Recall items per paper at ~25 sec each. Target: 7 correct in 5 min. If you don't recognise an allotrope or common-compound name within 5 sec, skip — the −1.33 penalty makes a guess negative-EV at below ~55% confidence.
- 7min
Sweep Rule (Atomic Structure + Acids/Bases + Reactions + Bonding)
Attempt every rule-application question. Periodic trends (1–2 q), pH/acid-base (1–2 q), redox identification (1–2 q), reaction type (1 q), ox-state assignment (≤1 q). ~6 items × ~60 sec. Target: 5 correct. If a redox question requires assigning ox-states to >2 elements in a complex compound, skip — those swallow 2+ min.
- 3min
Calculate last (Mole + Stoichiometry)
Tackle the numeric questions last. ~1 item most papers, sometimes 0. Set up the formula, plug numbers, double-check unit conversion. Don't get clever — Mole questions in NDA are direct plug-in, not multi-step. If the question gives you mass in g and asks for moles, divide by molar mass and you're done.
Recognition speed > knowledge depth. A 20-second pause on an allotrope question is fine; a 90-second pause is wasting your time budget. If you can’t place a compound by name within 10 seconds, skip — recall either fires fast or it doesn’t fire at all.
Time investment plan
| Strand | Hours | Outcome |
|---|---|---|
| Recall — Carbon + Matter + Industrial + Metals + Hydrogen + Everyday + Practical | 14 | ~24 marks/paper |
| Rule — Atomic Structure + Acids/Bases + Reactions + Bonding | 11 | ~17 marks/paper |
| Calculate — Mole Concept and Stoichiometry | 2 | ~2 marks/paper |
| Common-compounds active recall (the /common-compounds page) | 4 | Compounding gains across Recall |
| Past papers, timed (last 3 years) | 5 | Calibration + speed |
| Total | 36 | Target: 45+ marks (of 60 max) |
That’s about 5 weeks at 7 hours/week. The Recall strand gets the most hours (because it’s 7 chapters and the marks-per-hour leader); Common-compounds active recall sits alongside Recall as a dedicated cross-chapter pass. Calculate is small but distinct — don’t skip the 2 hours.
Start with the Recall strand — highest marks-per-hour
144 questions across 7 chapters at 4% average HARD. The bank’s marks-per-hour leader — bank these before touching anything calculation-heavy.