Titration curves Knowledge-Based Download PDF

Questions

1. 1.

   When a strong monoprotic acid is titrated with an equimolar strong monoprotic base, how does reducing the concentration of both solutions from 0.10 M to 0.010 M affect the resulting titration curve?

   • A) The vertical inflection region spans a narrower pH range, while the equivalence point pH remains 7.00 at 25 °C.
   • B) The vertical inflection region spans a wider pH range, and the equivalence point pH increases above 7.00 at 25 °C.
   • C) The initial pH of the solution decreases, causing the vertical inflection region to expand significantly.
   • D) The equivalence point pH increases to 8.00, while the span of the vertical inflection region remains unchanged.
2. 2.

   When comparing the titration curve of a weak monoprotic acid to that of an equimolar strong monoprotic acid of equal volume titrated with the same strong base, which difference is observed in the curve of the weak acid?

   • A) The weak acid requires a smaller volume of titrant to reach its equivalence point because it is only partially ionized.
   • B) The weak acid exhibits a lower initial pH and reaches an equivalence point with a pH below 7.0 at 25 °C.
   • C) The weak acid produces a much steeper and wider vertical inflection region around the equivalence point.
   • D) The weak acid exhibits a higher initial pH and a smaller vertical pH jump around the equivalence point.
3. 3.

   When a sample of a diprotic weak acid, $H_2A$, is titrated with a standardized strong monoprotic base, which relationship describes the total volume of base required to reach the second equivalence point ($V_2$) relative to the volume required to reach the first equivalence point ($V_1$)?

   • A) $V_2 = 2V_1$, because each proton neutralization stage requires an equal number of moles of base.
   • B) $V_2 = V_1$, because both acidic protons are neutralized simultaneously at the same volume.
   • C) $V_2 = 4V_1$, because neutralizing the second, weaker proton requires twice as much base volume per mole.
   • D) $V_2 = 1.5V_1$, because the second ionization occurs to only half the extent of the first ionization.
4. 4.

   During the titration of a weak base with a standard solution of a strong acid, which statement correctly describes the pH at the equivalence point and the chemical reason for this value?

   • A) The pH is equal to 7.00 because stoichiometric neutralization between an acid and a base always results in a neutral solution.
   • B) The pH is greater than 7.00 because the weak base establishes an alkaline buffer system at the equivalence point.
   • C) The pH is less than 7.00 because the conjugate acid produced undergoes hydrolysis to generate hydronium ions.
   • D) The pH is less than 7.00 because an excess of the strong acid titrant must be added to consume all the weak base.
5. 5.

   During the titration of a weak monoprotic acid with a standard solution of a strong base, which statement correctly describes a key feature of the titration curve?

   • A) The equivalence point occurs at a pH of exactly 7.00 because neutralization is complete.
   • B) The solution exhibits its minimum buffering capacity at the half-equivalence point.
   • C) The pH at the half-equivalence point is equal to the $pK_a$ of the weak acid.
   • D) The equivalence point has a pH below 7.00 due to the accumulation of hydronium ions.