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Chemistry Flashcards

7 cards from real MCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which of the following best describes a buffer solution?

    Answer: A solution that resists changes in pH when small amounts of acid or base are added

    A buffer resists pH changes because it contains a weak acid and its conjugate base (or weak base and conjugate acid) that can absorb added H⁺ or OH⁻.

  2. What is the hybridization of the carbon atom in CO₂?

    Answer: sp

    Carbon in CO₂ forms two double bonds with oxygen, requiring two sp hybrid orbitals and two unhybridized p orbitals for the π bonds.

  3. Which quantum number describes the shape of an orbital?

    Answer: Angular momentum quantum number (l)

    The angular momentum quantum number (l) determines the shape of the orbital: l=0 is s (spherical), l=1 is p (dumbbell), l=2 is d.

  4. A reaction has ΔG° = +20 kJ/mol at 298 K. Which statement is correct?

    Answer: The equilibrium constant K < 1

    A positive ΔG° means the reaction is non-spontaneous under standard conditions, and since ΔG° = -RT ln K, a positive ΔG° requires K < 1.

  5. In an SN2 reaction, the rate depends on which of the following?

    Answer: Both the concentration of the substrate and nucleophile

    SN2 is a bimolecular reaction with a concerted mechanism where the nucleophile attacks as the leaving group departs, so rate = k[substrate][nucleophile].

  6. Which of the following compounds would have the highest boiling point?

    Answer: CH₃OH

    Methanol (CH₃OH) has the highest boiling point because hydrogen bonding between OH groups is much stronger than the London dispersion forces in the hydrocarbons.

  7. The Henderson-Hasselbalch equation is used to calculate:

    Answer: The pH of a buffer solution given pKa and the ratio of conjugate base to acid

    Henderson-Hasselbalch states pH = pKa + log([A⁻]/[HA]), relating buffer pH to the pKa of the weak acid and the ratio of its conjugate base to acid.