Maharashtra HSC Chemistry, Reaction by Reaction
MSBSHSE Class 12 Chemistry worked through key reactions and numericals with full solutions, plus the section structure and chapter weightage that shapes an effective revision order.
Chemistry students in my classes tend to fall into one of two camps: the ones who treat it as pure memorisation and the ones who try to reason through everything from first principles. Neither approach alone works well for MSBSHSE's paper — you need memorised reactions and the reasoning to apply them to a slightly unfamiliar question. Let me show you what that combination actually looks like on a few representative problems.
The Paper's Shape
Seventy theory marks across five sections — MCQ (8), very short answer (12), short answer (12), longer short answer (16), and long answer (15, choose 3 of 4) — plus 30 practical marks handled separately at your college. No single section dominates the way some boards' papers do; steady preparation across the whole subject matters more here than concentrating on two or three chapters.
A Colligative Properties Problem, Worked Properly
9g of glucose dissolved in 250g of water. Find the freezing point depression. (Kf = 1.86 K·kg/mol)
Glucose's molar mass is 180 g/mol, so 9g gives us 9/180 = 0.05 mol. Molality — moles per kilogram of solvent, not per litre of solution, a distinction worth being precise about — is 0.05/0.25 = 0.2 mol/kg.
ΔTf = Kf×m = 1.86×0.2 = 0.372 K. The freezing point drops by that amount from water's normal 0°C, landing at −0.372°C.
The reasoning worth internalising: colligative properties depend on the number of solute particles, not their identity — which is exactly why this formula doesn't care that the solute happens to be glucose specifically. Swap in any non-electrolyte solute at the same molality and you'd get the identical depression.
Naming a Coordination Compound Correctly
Give the IUPAC name of [Fe(CN)₆]³⁻.
Central ion: Fe³⁺, iron in its +3 oxidation state. Six cyanide ligands (CN⁻) arranged octahedrally around it. IUPAC naming rules here: ligands get named first, alphabetically, followed by the metal, and since the overall complex ion is anionic, the metal's name takes the "-ate" suffix — iron becomes "ferrate." The oxidation state gets stated in Roman numerals at the end.
Full name: hexacyanidoferrate(III) ion. Students often get the pieces right individually — they know it's iron, they know there are six cyanides — but lose marks assembling them in the wrong order or forgetting the anionic "-ate" suffix. The naming convention is entirely rule-based, which means it's genuinely learnable through repetition rather than something you need to intuit.
A Reaction Worth Understanding, Not Just Memorising
How does a primary amine react with nitrous acid?
R−NH₂ + HNO₂ → R−N₂⁺Cl⁻ (unstable diazonium salt) → R−OH + N₂↑ + HCl
What makes this reaction genuinely useful to understand, beyond memorising the equation, is that it's a diagnostic test — the visible nitrogen gas evolution (brisk effervescence) distinguishes primary amines from secondary and tertiary amines, which behave differently under the same reagent. If a question describes an unknown compound producing gas bubbles with nitrous acid, that's your signal it's a primary amine, even before you've identified anything else about it. This is the kind of reaction MSBSHSE likes to test indirectly, through an application scenario, not just as a "write this equation" question.
Where Students Consistently Lose Marks
Confusing which colligative property formula applies when — freezing point depression and boiling point elevation use different constants (Kf vs Kb) and students under pressure sometimes reach for the wrong one despite knowing both individually.
Getting the pieces of a coordination compound's name right individually but assembling them in the wrong order, or forgetting the oxidation state's Roman numeral entirely.
Writing only the final product for a mechanism-based question, without showing the intermediate step — MSBSHSE's marking scheme specifically rewards the intermediate for nucleophilic addition and substitution reactions, not just the product.
What I'd Prioritise, Given Limited Time
Organic Chemistry — Haloalkanes, Alcohols, Carbonyl compounds — carries around 15 of the 70 theory marks, the single largest concentration in the syllabus, and it rewards genuinely understanding mechanisms rather than memorising products in isolation. If your remaining revision time is tight, that's where I'd point it first, followed by making sure every standard reaction you write leads with its balanced equation before any explanation — MSBSHSE awards marks for the equation independently of how well you explain what it means.