What the board asks
We went through the ISC board papers, question by question, and matched each question to a topic. Here is what was asked, how often, and what was never asked.
Chemistry: 384 topics in the 2027 syllabus, across 10 units. The board has asked 252 of them at least once. 132 were never asked in the papers we checked.
Pick a unit
C4 d- and f-Block Elements
All the topics in Chemistry: d- and f-Block Elements
Asked topics first, the most asked at the top. Tap a topic to see what to write, the result, the years, and the real board questions.
43 topics shown
| # | Topic | Type | Marks | Times asked | Last asked | Status |
|---|---|---|---|---|---|---|
| 1 | Give reasons: transition metal ions are coloured, some colourlessExplain colour by d-d transition of an unpaired electron absorbing visible light (the complementary colour is seen), and explain colourless ions by an empty (d0) or full (d10) d-subshell, using the ion's configuration. | Give reason | 1 | 7 papers | Specimen 2027 | Asked |
| 2 | Give reasons: paramagnetic vs diamagnetic ions and metalsWrite the configuration of each ion, count the unpaired electrons, and state that unpaired electrons make it paramagnetic (attracted to a magnetic field) while all-paired makes it diamagnetic. | Give reason | 1 | 5 papers | Specimen 2027 | Asked |
| 3 | Give reasons: consequences of lanthanoid contractionExplain, from lanthanoid contraction, why Zr and Hf (and Nb-Ta, Mo-W) have almost equal radii and are hard to separate, and why basic strength of Ln(OH)3 falls from La(OH)3 to Lu(OH)3. | Give reason | 1 | 5 papers | 2025 improvement | Asked |
| 4 | Acidified K2Cr2O7 with H2S, and its colour changeComplete and balance K2Cr2O7 + H2SO4 + H2S giving K2SO4, Cr2(SO4)3, water and sulphur, and state the colour change orange to green with a pale yellow precipitate. | Reaction | 1 | 4 papers | 2026 | Asked |
| 5 | Pick the coloured, colourless, para- or diamagnetic speciesFor each species in a list, find the oxidation state and d-configuration of the metal, then choose the one that fits the stated colour and magnetic behaviour, giving the one-line reason. | Comparison | 1 | 3 papers | Specimen 2027 | Asked |
| 6 | Give reasons: transition metals readily form alloysState that transition metals have similar atomic radii, so atoms of one can take the place of another in the crystal lattice (they are miscible when molten), and name one alloy. | Give reason | 1 | 3 papers | Specimen 2027 | Asked |
| 7 | Give reasons: KMnO4 decolourises; self-indicator in titrationsExplain why pink KMnO4 turns colourless with Fe2+ or warm oxalic acid (MnO4- reduced to nearly colourless Mn2+), why it acts as its own indicator, and why H2SO4, not HCl or HNO3, is used to acidify. | Give reason | 1 | 3 papers | 2026 | Asked |
| 8 | Colour changes and gases in KMnO4 and K2Cr2O7 reactionsFrom a short description of a reaction of KMnO4 or K2Cr2O7, choose or fill in the colour change, the gas evolved or the product, giving the one-line reason from the change in oxidation state. | Comparison | 1 | 3 papers | 2026 | Asked |
| 9 | Acidified KMnO4 with oxalic acidComplete and balance KMnO4 + H2SO4 + oxalic acid, warmed to about 60 C, giving K2SO4, MnSO4, CO2 and water, and name the gas. | Reaction | 1 | 3 papers | 2025 | Asked |
| 10 | Acidified KMnO4 with KIComplete and balance KMnO4 + H2SO4 + KI giving K2SO4, MnSO4, I2 and water, and state that iodine is liberated. | Reaction | 1 | 3 papers | 2025 improvement | Asked |
| 11 | Give reasons: variable oxidation states; Mn2+ vs Fe2+ stabilityExplain variable valency by the close energies of (n-1)d and ns electrons, list common oxidation states for a 3d element, and compare the stability of two ions using half-filled or filled d configurations. | Give reason | 1 | 3 papers | 2024 | Asked |
| 12 | Give reasons: high melting points; low for Zn, Cd, HgLink melting point and hardness to the strength of metallic bonding from the number of unpaired (n-1)d and ns electrons, and explain the low values of Zn, Cd and Hg by their fully paired d10 electrons. | Give reason | 1 | 2 papers | Specimen 2027 | Asked |
| 13 | Acidified KMnO4 with H2SComplete and balance KMnO4 + H2SO4 + H2S giving K2SO4, MnSO4, water and sulphur, and name the yellow precipitate of sulphur. | Reaction | 1 | 2 papers | Specimen 2027 | Asked |
| 14 | Give reasons: K2Cr2O7 is a strong oxidant in acidWrite the equation of K2Cr2O7 with dilute H2SO4 giving 3 nascent oxygen atoms (or the ionic half-equation gaining 6 electrons) and state that Cr goes from +6 to +3. | Give reason | 1 | 2 papers | Specimen 2027 | Asked |
| 15 | Acidified KMnO4 with FeSO4 (or Mohr's salt)Complete and balance the full molecular equation of KMnO4 with FeSO4 in dilute H2SO4, giving all four products, and the ionic equation if asked. | Reaction | 1 | 2 papers | 2026 | Asked |
| 16 | Acidified K2Cr2O7 with KIComplete and balance K2Cr2O7 + H2SO4 + KI giving K2SO4, Cr2(SO4)3, I2 and water. | Reaction | 1 | 2 papers | 2026 | Asked |
| 17 | Assertion-reason items on lanthanoid contractionJudge the truth of the assertion and of the reason separately, then decide whether the reason correctly explains the assertion, writing the chosen option with a one-line justification. | Give reason | 1 | 2 papers | 2025 improvement | Asked |
| 18 | KMnO4 or K2Cr2O7 with SO2 or sodium sulphiteComplete and balance the oxidation of sulphite (or SO2) to sulphate by acidified K2Cr2O7 or by KMnO4, giving all products. | Reaction | 1 | 2 papers | 2025 improvement | Asked |
| 19 | Give reasons: Zn, Cd, Hg are not transition elementsWrite the d10 configuration of the atom and its common +2 ion and state that neither has an incompletely filled d-subshell, so it is d-block but not transition. | Give reason | 1 | 2 papers | 2024 | Asked |
| 20 | Give reasons: transition metals and compounds act as catalystsState the two reasons, variable oxidation states (forming unstable intermediates) and a large surface for adsorption, and name one example with its process. | Give reason | 1 | 2 papers | 2023 | Asked |
| 21 | Give reasons: trend in radii and density across 3d seriesState that radii fall then level off across the series because increasing nuclear charge is partly cancelled by poor d shielding, and that density rises from Ti to Cu because mass increases while volume decreases. | Give reason | 1 | 2 papers | 2020 | Asked |
| 22 | Compare ionisation enthalpies of 3d elements with reasonCompare the first (or second) ionisation enthalpies of two given 3d elements and justify with their configurations, nuclear charge, and the stability of half-filled or filled subshells. | Comparison | 1 | 1 paper | 2026 | Asked |
| 23 | Give reasons: transition metals form complexesGive the three reasons, small highly charged ions, vacant (n-1)d orbitals of suitable energy to accept lone pairs, and variable oxidation states, with one example complex. | Give reason | 1 | 1 paper | 2024 | Asked |
| 24 | Give reasons: colour, complexes and alloys of lanthanoidsExplain colour of Ln3+ ions by f-f transitions of unpaired f electrons and the colourless La3+ (4f0) and Lu3+ (4f14), state why lanthanoids form few complexes (large ions, low charge density), and name misch metal. | Give reason | 1 | 1 paper | 2024 | Asked |
| 25 | Lanthanoid contraction: meaning and causeDefine the steady decrease in atomic and ionic radii from La to Lu and give its cause, the poor shielding by 4f electrons of the increasing nuclear charge, and pick the largest or smallest Ln3+ ion. | Statement | 1 | 1 paper | 2019 | Asked |
| 26 | Acidified K2Cr2O7 with FeSO4Complete and balance K2Cr2O7 + H2SO4 + FeSO4 giving K2SO4, Cr2(SO4)3, Fe2(SO4)3 and water, and the ionic equation if asked. | Reaction | 1 | 1 paper | 2019 | Asked |
| 27 | Position, occurrence and definition of transition elementsDefine a transition element, place the d-block (groups 3-12) and f-block in the periodic table with the four d-series and two f-series, and name one ore of a common 3d metal. | Statement | 1 | never | Never asked | |
| 28 | Electronic configuration of 3d atoms and ions, unpaired electronsWrite the full (n-1)d ns configuration of a given 3d atom or ion, removing 4s electrons first for ions, and count the unpaired d electrons. | Structure or name | 1 | never | Never asked | |
| 29 | Interstitial compounds: meaning, examples and propertiesDefine an interstitial compound as small atoms (H, C, N, B) trapped in the metal lattice, give two examples, and state two properties with reasons (hard, high m.p., conducting, non-stoichiometric). | Statement | 1 | never | Never asked | |
| 30 | Lanthanoids and actinoids: configuration and oxidation statesWrite the general configurations 4f1-14 5d0-1 6s2 and 5f1-14 6d0-1 7s2, state that +3 is the common lanthanoid state, and explain Ce4+, Eu2+ and Yb2+ by the stability of f0, f7 and f14. | Structure or name | 1 | never | Never asked | |
| 31 | Lanthanoid reactions with O2, H2, halogens, S, N, C, waterWrite the product and a balanced equation, with heating condition, for a lanthanoid reacting with each of oxygen, hydrogen, a halogen, sulphur, nitrogen, carbon and water. | Reaction | 2 | never | Never asked | |
| 32 | Actinoids: oxidation states and comparison with lanthanoidsState that actinoids show a wider range of oxidation states (+3 to +7) because 5f, 6d and 7s energies are close, and give three points of contrast with lanthanoids (oxidation states, radioactivity, complex formation, actinoid contraction). | Comparison | 2 | never | Never asked | |
| 33 | Structure and shape of the permanganate ionDraw MnO4- as a tetrahedron with Mn at the centre, one Mn-O(-) and three Mn=O shown (or resonance), state Mn is +7 and the ion is tetrahedral and diamagnetic. | Structure or name | 1 | never | Never asked | |
| 34 | KMnO4 from pyrolusite: equations of preparationWrite the balanced equations for fusing MnO2 with KOH in air (or with KNO3) to green K2MnO4, and for converting manganate to permanganate by disproportionation in acid or by electrolytic oxidation, with conditions. | Reaction | 2 | never | Never asked | |
| 35 | KMnO4 as oxidant: nascent oxygen and electrons gainedWrite the nascent-oxygen equation (or ionic half-equation) for KMnO4 in acidic, neutral and alkaline medium and give the electrons gained (5, 3, 3) and the Mn product (Mn2+ or MnO2) in each. | Give reason | 1 | never | Never asked | |
| 36 | Alkaline KMnO4 with KIWrite the balanced equation of KMnO4 with KI in alkaline (or neutral) solution giving MnO2, KOH and potassium iodate, and state the change in oxidation state of Mn (+7 to +4). | Reaction | 1 | never | Never asked | |
| 37 | Neutral KMnO4 with H2SWrite the balanced equation of KMnO4 with H2S in neutral solution giving MnO2, KOH, sulphur and water. | Reaction | 1 | never | Never asked | |
| 38 | Structures and shapes of chromate and dichromate ionsDraw CrO4^2- as a tetrahedron and Cr2O7^2- as two tetrahedra sharing one corner oxygen (Cr-O-Cr), state the oxidation state of Cr (+6) and the colours. | Structure or name | 1 | never | Never asked | |
| 39 | K2Cr2O7 from chromite ore: equations of preparationWrite the three balanced steps, fusing chromite with Na2CO3 in air to sodium chromate, acidifying to sodium dichromate, and double decomposition with KCl to K2Cr2O7, with conditions. | Reaction | 2 | never | Never asked | |
| 40 | Chromate-dichromate interconversion and effect of pHWrite the equations for chromate turning to dichromate in acid and back in alkali, give the colour change, and explain the shift by the pH of the solution. | Reaction | 1 | never | Never asked | |
| 41 | K2Cr2O7 in neutral and alkaline mediumState that in alkali dichromate changes to chromate, and write the half-equation for chromate as a weak oxidant in neutral or alkaline solution giving Cr(OH)3, with the change in oxidation state of Cr. | Statement | 1 | never | Never asked | |
| 42 | Use of K2Cr2O7 in redox titrationsState that K2Cr2O7 is a primary standard (pure, stable, not hygroscopic), that an internal indicator such as diphenylamine is needed because it is not a self-indicator, and write the titration equation with Fe2+. | Statement | 1 | never | Never asked | |
| 43 | Spin-only magnetic moment of a 3d ionWrite the ion's configuration, count unpaired electrons n, substitute in mu = sqrt(n(n+2)) BM and give the value to two decimals; or work back from mu to n. | Numericals | 1 | never | Not in syllabus |
This list was made from the 2027 syllabus and checked with 9 board papers, including the 2027 specimen paper. It is not yet checked with the textbook.
The 10 topics Chemistry papers ask most
Counted on the board papers from 2018 to the 2027 specimen paper, which every unit has been checked against.
- 1.IUPAC names of coordination compounds from formulaC5 Coordination Compounds · asked 8 times since 2018
- 2.Faraday's first law: mass, charge, current or timeC2 Electrochemistry · asked 7 times since 2018
- 3.Give reasons: transition metal ions are coloured, some colourlessC4 d- and f-Block Elements · asked 7 times since 2018
- 4.Alcohols from Grignard reagent: 1, 2, 3 degreeC7 Alcohols, Phenols and Ethers · asked 7 times since 2018
- 5.Williamson's synthesis of ethersC7 Alcohols, Phenols and Ethers · asked 7 times since 2018
- 6.Identify A, B, C, D in a given reagent chainC8 Aldehydes, Ketones and Carboxylic Acids · asked 7 times since 2018
- 7.Identify compounds from formula and test results (case problem)C8 Aldehydes, Ketones and Carboxylic Acids · asked 7 times since 2018
- 8.Identify A, B, C: amide, Hoffmann and amine-test chainsC9 Organic Compounds containing Nitrogen · asked 7 times since 2018
- 9.Gibbs energy and maximum work from cell emfC2 Electrochemistry · asked 6 times since 2018
- 10.Coordination number and oxidation state of the central metalC5 Coordination Compounds · asked 6 times since 2018