Chemistry MDCAT
Organic, inorganic & physical chemistry MCQs
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Total MCQs
Chemistry
MDCAT Chemistry MCQs — organic, inorganic & physical chemistry
Answer: MgO has the highest lattice energy due to the small ionic radii and high charges (+2 and -2) of Mg2+ and O2-, resulting in very strong electrostatic attractions.
Answer: In Fe2O3: 2(Fe) + 3(-2) = 0, so 2Fe = 6, Fe = +3.
Answer: Ethyne (acetylene, C2H2) contains a carbon-carbon triple bond (C≡C), making it an alkyne.
Answer: MnO2 oxidizes HCl to produce Cl2: MnO2 + 4HCl -> MnCl2 + Cl2 + 2H2O. Here MnO2 is the oxidizing agent.
Answer: Propanone has the structure CH3COCH3. The carbonyl group is at carbon 2, so its IUPAC name is propan-2-one (commonly called acetone).
Answer: Primary alkyl halides favor SN2 because they have minimal steric hindrance, and strong nucleophiles with polar aprotic solvents further promote bimolecular substitution.
Answer: As Q increases, the logarithmic term (RT/nF)lnQ becomes more positive, which reduces E from E0, decreasing the cell potential.
Answer: At constant pressure, q = Delta H. Since heat is released (exothermic), Delta H = -200 J by sign convention.
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Answer: Rate = k[A]^n. If 2^n = 4, then n = 2, meaning the reaction is second order with respect to A.
Answer: CN- is a strong field ligand at the top of the spectrochemical series, causing the largest crystal field splitting (Delta_o).
Answer: SN1 proceeds through a planar carbocation intermediate. Nucleophilic attack from both faces gives racemization, but ion pairing often causes slight excess inversion.
Answer: SN2 is bimolecular: both the substrate and nucleophile are involved in the rate-determining step, so Rate = k[CH3Br][OH-].
Answer: Six NH3 ligands give coordination number 6. Each NH3 is neutral and 3 Cl- balance the charge, so Co is +3.
Answer: The complex can exist as cis (Cl ligands adjacent) and trans (Cl ligands opposite) geometric isomers due to its octahedral geometry.
Answer: Hess\'s law states that the total enthalpy change for a reaction is the same regardless of whether it occurs in one step or multiple steps, because enthalpy is a state function.
Answer: E2 requires an anti-periplanar arrangement where the C-H and C-LG bonds are at 180 degrees, allowing maximum orbital overlap for the developing pi bond.
Answer: At equilibrium, Q = K and Delta G = 0, so from Delta G = -nFE, we get E = 0. The cell has no driving force at equilibrium.
Answer: IR spectroscopy measures the absorption of infrared radiation by molecular vibrations (stretching and bending of bonds), revealing functional groups and molecular framework.
Answer: Chemical shift reflects the shielding/deshielding of a proton by surrounding electrons. Deshielded protons (near electronegative atoms) appear at higher delta values.
Answer: E1 is unimolecular: only the substrate is involved in the rate-determining step (carbocation formation), so Rate = k[substrate], making it first order.