23 practice MCQs on dynamic equilibrium, Le Chatelier's principle, Kc and Kp, pH, buffers and acid-base theories. Every question has the correct answer and an explanation.
Start free — 20 questionsChemical Equilibrium and Acids and Bases is part of the MDCAT Chemistry syllabus. This page collects Chemical Equilibrium and Acids and Bases MCQs in the style of past MDCAT papers — below are 12 of them with answers and explanations, and the full set of 23 questions is in the HighYield MDCAT QBank.
This chapter covers: dynamic equilibrium, Le Chatelier's principle, Kc and Kp, pH, buffers and acid-base theories.
Correct answer: B. pH
A buffer solution resists significant change in pH when small amounts of acid or base are added, due to the presence of a conjugate acid-base pair.
Correct answer: D. 7.35 – 7.4
Normal human blood pH is tightly maintained within the range of 7.35 to 7.4, slightly alkaline.
Correct answer: C. 11
A 10⁻³ M NaOH solution gives [OH-] = 10⁻³ M, so pOH = 3 and pH = 14 - 3 = 11.
Correct answer: B. Ksp = [Ag⁺][Cl⁻]
For the dissociation AgCl to Ag+ + Cl-, the solubility product is Ksp = [Ag+][Cl-], the product of the ion concentrations (the solid is excluded).
Correct answer: C. 1.6 × 10⁻⁸ mol²dm⁻⁶
The solubility product (Ksp) of PbSO4 at 25°C is approximately 1.6 × 10⁻⁸ mol²dm⁻⁶, reflecting its low solubility.
Correct answer: B. 5.6
Unpolluted natural rainwater has a pH of approximately 5.6, slightly acidic due to dissolved carbon dioxide forming carbonic acid.
Correct answer: C. Reaction must be carried out at low temperature
Since the reaction 2NO + O2 ⇌ 2NO2 is exothermic (ΔH negative), Le Chatelier's principle predicts that lower temperatures favour the forward reaction, increasing NO2 yield, so the reaction should be carried out at low temperature.
Correct answer: B. Cation
At low pH (acidic conditions), amino acids exist predominantly as cations, with both the amino and carboxyl groups protonated.
Correct answer: A. Le Chatelier's principle
Le Chatelier's principle is a concept that helps in predicting the direction in which a system at equilibrium will shift in response to a change in conditions.
Correct answer: B. Product side
Product side: Correct answer—When the product is removed in a reversible reaction, the equilibrium shifts toward the product side to produce more product, according to Le Chatelier's principle.
Correct answer: D. HCl
If you want to turn the cloudy solution (which indicates the presence of BiOCl) into a clear solution, you can add an excess of HCl. This addition will cause the equilibrium to shift to the right, reducing the amount of BiOCl and potentially dissolving it, thereby clarifying the solution.
Correct answer: B. 7.35
The pH of human blood is typically maintained between 7.35 and 7.45. This range is slightly basic, as a pH of 7 is considered neutral. The body has several mechanisms to regulate blood pH tightly, including the bicarbonate buffer system. Option B, 7.35, falls within this normal range. Option A, 7.80, is too alkaline for blood, whereas Options C, D, and E (7.33, 6.62, 7.05) are too acidic, indicating varying degrees of acidosis.
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