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MCAT General Chemistry: Equilibrium, Acids, Bases and Thermodynamics — quiz

15 multiple-choice questions covering Equilibrium Basics, Le Chatelier's Principle, Acid-Base Equilibria, Buffers, Titrations. One answer each; you get a score at the end and the explanation for every question. No account needed.

Updated 2026-11-04. Keys 1–4 pick an answer, Enter moves on. Redo it any time, in order or shuffled.

The questions

Answers and explanations are shown after you finish.

1. Equilibrium Basics

   A reaction mixture has Q = 0.5 while Keq = 2.0 for the same reaction. What will happen next?

   • The shift direction cannot be determined from Q and Keq alone
   • No shift, because the system is already at equilibrium
   • Forward, toward products, because Q is less than Keq
   • Reverse, toward reactants, because Q is less than Keq
2. Le Chatelier's Principle

   For the gas-phase equilibrium 2SO2(g) + O2(g) ⇌ 2SO3(g), the container volume is suddenly decreased. Which way does the equilibrium shift?

   • Reverse, toward SO2 and O2, because that side has fewer total moles
   • Forward, toward SO3, because that side has fewer total moles of gas
   • No shift, since Keq is independent of pressure changes
   • Forward, toward SO3, because the forward reaction is exothermic
3. Le Chatelier's Principle

   An exothermic reaction is at equilibrium and the temperature is raised. What happens?

   • Equilibrium shifts toward products and Keq stays the same
   • Equilibrium shifts toward products and Keq increases
   • Equilibrium position is unaffected but the rate of reaction increases
   • Equilibrium shifts toward reactants and Keq decreases
4. Acid-Base Equilibria

   A weak base has Kb = 1.0×10⁻⁴. What is the Ka of its conjugate acid at 25°C?

   • 1.0×10⁻¹⁸
   • 1.0×10⁻⁴
   • 1.0×10¹⁰
   • 1.0×10⁻¹⁰
5. Acid-Base Equilibria

   Acid X has pKa = 3.2 and acid Y has pKa = 5.8. Which is the stronger acid and why?

   • Acid X, because a lower pKa corresponds to a smaller Ka
   • Acid Y, because a higher pKa means more complete dissociation
   • Acid X, because a lower pKa corresponds to a larger Ka and stronger acid
   • Neither; pKa does not relate to acid strength
6. Buffers

   A buffer has pKa = 4.76 and a ratio [A⁻]/[HA] = 0.1. What is the pH?

   • 4.66
   • 5.76
   • 4.76
   • 3.76
7. Titrations

   At the equivalence point of a weak acid–strong base titration, why is the pH greater than 7?

   • Excess strong base remains unreacted in solution
   • Strong base is a better electrolyte than the weak acid
   • The conjugate base formed hydrolyzes water, producing OH⁻
   • The weak acid releases OH⁻ ions upon full dissociation
8. Titrations

   During a weak acid–strong base titration, at what point does pH equal pKa, and why?

   • At the half-equivalence point, because all the acid has been converted to its conjugate base
   • At the half-equivalence point, because [HA] equals [A⁻] there
   • At the start of titration, before any base is added
   • At the equivalence point, because [HA] equals [A⁻] there
9. Thermodynamics

   A reaction has ΔH > 0 and ΔS < 0. Under what conditions is it spontaneous?

   • Never spontaneous, at any temperature
   • Spontaneous only at low temperatures
   • Spontaneous only at high temperatures
   • Always spontaneous, at any temperature
10. Thermodynamics

    A reaction has a very large equilibrium constant K. What can be concluded about ΔG°?

    • ΔG° cannot be determined without temperature
    • ΔG° is large and positive
    • ΔG° equals zero
    • ΔG° is large and negative
11. Kinetics

    In a kinetics experiment, doubling the concentration of reactant A (with B held constant) causes the rate to quadruple. What is the reaction order with respect to A?

    • 1
    • 0
    • 4
    • 2
12. Electrochemistry

    In a galvanic cell, what occurs at the anode and what is its charge?

    • Oxidation occurs there, and it carries a negative charge
    • Oxidation occurs there, and it carries a positive charge
    • Reduction occurs there, and it carries a positive charge
    • Reduction occurs there, and it carries a negative charge
13. Gases

    A gas sample occupies 10 L at 300 K and 2 atm. If the temperature is raised to 600 K while pressure is held constant, what is the new volume?

    • 10 L
    • 5 L
    • 20 L
    • 40 L
14. Solubility

    Sodium chloride is added to a saturated solution of silver chloride (AgCl). What happens to the solubility of AgCl?

    • Solubility decreases due to the common ion effect
    • Solubility increases due to higher ionic strength
    • Solubility increases because Cl⁻ forms a soluble complex with Ag+
    • Solubility is unchanged because Na+ is a spectator ion
15. Colligative Properties

    A 2 m aqueous solution of CaCl2 (i = 3) is prepared, with Kf = 1.86 °C/m for water. What is the freezing point depression?

    • 1.86°C
    • 11.16°C
    • 3.72°C
    • 5.58°C