Buffers Knowledge-Based Practice

Questions

1. 1.

   When a small amount of a strong acid is added to an aqueous buffer solution composed of a weak acid ($\text{HA}$) and its conjugate base ($\text{A}^-$), how do the concentrations of the buffer components shift as equilibrium is reestablished?

   • A) The concentration of $\text{A}^-$ decreases while the concentration of $\text{HA}$ increases.
   • B) The concentration of $\text{A}^-$ increases while the concentration of $\text{HA}$ decreases.
   • C) The concentrations of both $\text{HA}$ and $\text{A}^-$ decrease simultaneously as they are neutralized.
   • D) The concentrations of both $\text{HA}$ and $\text{A}^-$ remain completely unchanged because buffers resist change.
2. 2.

   A biological buffer system exhibits its greatest capacity to resist pH changes in both directions under which of the following conditions?

   • A) When the concentration of the weak acid greatly exceeds that of its conjugate base
   • B) When all dissolved weak acid molecules completely dissociate into free hydrogen ions
   • C) When the concentrations of the weak acid and its conjugate base are approximately equal
   • D) When the solution is maintained at a neutral pH of exactly 7.0 regardless of the buffer's components
3. 3.

   Which of the following chemical pairs is fundamentally required to establish a functional buffer solution in a biological system?

   • A) A strong acid and its conjugate base
   • B) A strong acid and an equimolar strong base
   • C) A weak acid and its conjugate base
   • D) A nonpolar organic solvent and an insoluble mineral salt
4. 4.

   In human blood, the carbonic acid–bicarbonate buffer system maintains pH homeostasis. When an influx of hydroxide ions ($\text{OH}^-$) enters the bloodstream, which chemical component directly neutralizes these ions, and what is produced as a result?

   • A) Carbonic acid ($\text{H}_2\text{CO}_3$), producing bicarbonate ($\text{HCO}_3^-$) and water
   • B) Bicarbonate ($\text{HCO}_3^-$), producing carbonic acid ($\text{H}_2\text{CO}_3$) and hydronium ions
   • C) Carbon dioxide ($\text{CO}_2$), producing carbonate ions and water
   • D) Bicarbonate ($\text{HCO}_3^-$), producing carbon dioxide and hydrogen gas
5. 5.

   Which of the following best describes how a biological buffer system maintains a relatively constant pH in an aqueous solution?

   • A) By completely ionizing in water to permanently remove all hydrogen ions
   • B) By reversibly binding or releasing hydrogen ions in response to changes in pH
   • C) By converting excess hydroxide ions into nonpolar molecules through dehydration reactions
   • D) By precipitating strong acids out of biological fluids as insoluble salts

Answers and step-by-step solutions appear after you finish the test.