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Daily Mains answer writing

One chemistry question a day from the syllabus common to UPSC Civil Services (Chemistry optional), IFoS and Combined Geo-Scientist Mains. Write it by hand in the given time, then check yourself against the model answer that appears here the next morning.

How to use it

  1. Read the question at 7 AM here or on Telegram.
  2. Write by hand in the time shown, about 7 minutes for a 10-marker, with a diagram or equation wherever it earns marks.
  3. Next morning, open the model answer and tick off the marking points you covered.

All questions 15 so far

  1. 18-electron rule and synergic bonding in metal carbonyls; ν(CO) of [V(CO)₆]⁻, Cr(CO)₆, [Mn(CO)₆]⁺ Organometallic chemistryAnswer tomorrow
  2. Hückel's rule and Frost circles: why cyclopentadiene is acidic and tropylium bromide is ionic AromaticityModel answer
  3. UV spectra of enones: π→π* and n→π* bands, λmax of mesityl oxide and cyclohex-2-enone SpectroscopyModel answer
  4. Particle in a 1D box: energy levels and the λmax of 1,3-butadiene Quantum chemistryModel answer
  5. VSEPR: shapes of ClF₃, SF₄ and XeF₄, and where the lone pairs go Chemical bondingModel answer
  6. Beckmann rearrangement: mechanism with acetophenone oxime, and why it is stereospecific RearrangementsModel answer
  7. Quantum yield: why H₂ + Cl₂ has φ ≈ 10⁶ but H₂ + Br₂ only about 0.01 PhotochemistryModel answer
  8. Packing efficiency of bcc, and why CsCl is 8:8 while NaCl is 6:6 Solid stateModel answer
  9. Nernst equation: EMF, ΔG and K of the Daniell cell at given concentrations ElectrochemistryModel answer
  10. Distinguish ethanol and dimethyl ether by IR and ¹H NMR spectroscopy SpectroscopyModel answer
  11. Derive the Clausius–Clapeyron equation; boiling point of water at 0.5 atm Thermodynamics and phase equilibriaModel answer
  12. MO diagram of NO: why NO⁺ has a shorter bond and higher stretching frequency Chemical bondingModel answer
  13. Neopentyl bromide: why SN2 is very slow and solvolysis gives rearranged products Reaction mechanismsModel answer
  14. First-order reaction: show t₉₉.₉% is about ten half-lives, and a numerical Chemical kineticsModel answer
  15. Why is [Co(NH₃)₆]³⁺ diamagnetic but [CoF₆]³⁻ paramagnetic? CFSE of both Coordination chemistryModel answer