Chemistry MDCAT MCQs
Organic, inorganic & physical chemistry MCQs
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221
Which of the following is the correct order of reactivity for elimination (E2) with 2-bromobutane?
Answer: E2 reactivity increases with alkyl substitution because more substituted alkenes (Zaitsev product) are more stable, and tertiary substrates have more beta-hydrogens.
Answer: 1H NMR gives different splitting patterns: 1-propanol shows a triplet for the CH3, while 2-propanol shows a distinctive septet for the CH and a doublet for two equivalent CH3 groups.
Answer: The spin-only formula gives magnetic moment mu = sqrt(n(n+2)) Bohr magnetons, where n is the number of unpaired electrons.
Answer: A bidentate ligand has two donor atoms that simultaneously coordinate to the metal center, forming a chelate ring (e.g., ethylenediamine, oxalate).
Answer: The De Broglie equation states lambda = h/p = h/(mv), where h is Planck\'s constant, m is mass, and v is velocity, predicting wave-particle duality.
Answer: Standard enthalpy of combustion is the enthalpy change when 1 mole of a substance undergoes complete combustion in excess O2 under standard conditions (298 K, 1 atm).
Answer: In high-spin d5, each of the five d-orbitals gets one electron (t2g3 eg2) with no pairing, so no pairing energy is required.
Answer: Numbering gives the double bond the lowest locant: C1=C2-C3(Br)-C4. Bromine is on C3, so the name is 3-bromobut-1-ene.
Answer: Sigma bonds are the strongest, so sigma -> sigma* transitions require the highest energy (shortest wavelength), typically in the far UV region.
Answer: For first-order reactions, t1/2 = ln(2)/k = 0.693/k, which is independent of the initial concentration.
Answer: The slowest step in SN1 is ionization: the departure of the leaving group to form a carbocation intermediate. This step has the highest activation energy.
Answer: As T increases, Ea/RT decreases, making e^(-Ea/RT) larger, so k increases exponentially with temperature.
Answer: Tetrafluoroethylene (CF2=CF2) undergoes addition polymerization to form PTFE (Teflon), where the double bond opens to form long chains.
Answer: Kp = Kc(RT)^(Delta n). Delta n = 2 - (1+3) = -2, so Kp = Kc(RT)^(-2) = Kc/(RT)^2.
Answer: Hot, concentrated KMnO4 is a strong oxidizing agent that cleaves the C=C double bond in cyclohexene, oxidizing it completely to adipic acid (HOOC-CH2-CH2-CH2-CH2-COOH).
Answer: The SN2 transition state has a pentacoordinate carbon with the nucleophile and leaving group on opposite sides, forming a trigonal bipyramidal arrangement.
Answer: Faraday\'s first law: mass deposited (m) = (M x I x t)/(n x F), where M is molar mass, I is current, t is time, n is electrons transferred, and F = 96485 C/mol.
Answer: Molecularity is the number of molecules that come together in an elementary step. Three simultaneous collisions give termolecular (trimolecular) molecularity.
Answer: The salt formed (e.g., NaCl) is neutral, so the pH at equivalence is exactly 7 for strong acid-strong base titrations.
Answer: HBr adds across the C=C double bond in propene. The electrophilic H+ attacks the pi bond first, followed by nucleophilic Br- attack.