Class 12 Chemistry – Daily Revision MCQ (English Medium)
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At constant temperature and pressure, a process is spontaneous when the Gibbs energy change of the system (ΔG) is:
Chapter 4: Chemical Thermodynamics
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Answer: C. negative
In a spontaneous process at constant T and P the Gibbs energy of the system decreases, so ΔG < 0 (ΔG = 0 means equilibrium).A gas expands freely into a vacuum (free expansion). The work done by the gas is:
Chapter 4: Chemical Thermodynamics
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Answer: A. zero
In a vacuum there is no opposing pressure (Pext = 0), so W = −Pext ΔV = 0.Among the noble gases present in dry air, which one is the major constituent?
Chapter 7: Elements of Groups 16, 17 and 18
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Answer: B. Argon
Noble gases make up about 1% by volume of dry air, and argon is the major one among them.Sulphur shows +4 and +6 oxidation states, but oxygen cannot show such higher oxidation states because oxygen:
Chapter 7: Elements of Groups 16, 17 and 18
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Answer: A. has no vacant d orbitals
Oxygen has no d orbitals in its valence shell, so it cannot expand its octet to reach higher oxidation states.Using the spin-only formula, the magnetic moment of a transition metal ion having 3 unpaired electrons is about:
Chapter 8: Transition and Inner transition Elements
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Answer: D. 3.87 BM
μ = √(n(n + 2)) = √(3 × 5) = √15 ≈ 3.87 BM.The steady decrease in atomic and ionic radii from lanthanum (La) to lutetium (Lu) is called:
Chapter 8: Transition and Inner transition Elements
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Answer: B. lanthanoid contraction
Across the lanthanoid series the radii decrease steadily from La to Lu; this is known as lanthanoid contraction.With Lucas reagent (conc. HCl + anhydrous ZnCl₂), which alcohol turns the solution turbid instantly at room temperature?
Chapter 11: Alcohols, Phenols and Ethers
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Answer: D. 2-Methylpropan-2-ol
2-Methylpropan-2-ol is a tertiary alcohol; tertiary alcohols react fast and turn Lucas reagent turbid instantaneously (secondary slowly, primary only on heating).The Cannizzaro reaction is given only by aldehydes that have no α-hydrogen. Which of these aldehydes can undergo it?
Chapter 12: Aldehydes, Ketones and Carboxylic acids
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Answer: C. Benzaldehyde
Benzaldehyde (C₆H₅CHO) has no α-hydrogen; ethanal, propanal and butanal all have α-hydrogens.Nylon 6,6 is obtained by condensation polymerisation of:
Chapter 15: Introduction to Polymer Chemistry
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Answer: A. adipic acid and hexamethylenediamine
Adipic acid and hexamethylenediamine first form nylon salt, which on condensation polymerisation gives the polyamide nylon 6,6.PHBV, an aliphatic polyester that is degraded by microbes, is a copolymer of:
Chapter 15: Introduction to Polymer Chemistry
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Answer: B. 3-hydroxybutanoic acid and 3-hydroxypentanoic acid
PHBV = poly(β-hydroxybutyrate-co-β-hydroxyvalerate), made from 3-hydroxybutanoic acid and 3-hydroxypentanoic acid joined by ester links.
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All questions are written by PadhaiNotes in our own words from the chapters of the official Maharashtra State Board Balbharati textbook (ebalbharati.in). Each question shows its chapter.