Consider the titration curve for aqueous ammonia shown below. The quantity of hydrochloric acid required to reach the equivalence point in the titration is:

Question

Consider the titration curve for aqueous ammonia shown below.  The quantity of hydrochloric acid required to reach the equivalence point in the titration is:

Quizplus · Accepted Answer

11ecba2d_11fd_99f9_a3bf_f931798dbed8_MD0008_00 In an acid-base titration, a measured amount of an acid (or a base) solution (titrant) with a known concentration is slowly added to another solution containing a base (or an acid) of an unknown concentration to be determined. The acid (or base) being titrated is fully neutralized at the equivalence point, where the number of equivalents of acid exactly equals the number of equivalents of base. The pH changes rapidly when passing through the equivalence point. On a titration curve, this is seen as a nearly vertical segment, and the equivalence point is located at the middle of this vertical segment. The quantity (moles) of acid or base delivered at this point is calculated by multiplying the volume of titrant added by the titrant concentration. In this titration, 100 mL of 0.1 M HCl were required to reach the equivalence point. Accordingly, the number of millimoles of HCl required to reach this point is 11ecba2d_11fd_99fa_a3bf_77b2235dd538_MD0008_00 Because each mole of ammonia gives one equivalent of base and each mole of HCl gives one equivalent of acid, the neutralization reaction in this titration proceeds with a 1:1 molar ratio. Therefore, 10 mmol of HCl were required to neutralize 10 mmol of NH₃ present in the unknown ammonia solution. (Choices A, C, and D) Quantities of 9 mmol, 12 mmol, and 16 mmol result from adding 90 mL, 120 mL, and 160 mL of 0.1 M HCl, respectively, to the ammonia solution. These volumes of titrant are less than or greater than the volume required to reach the equivalence point. Educational objective: The equivalence point in an acid-base titration occurs when the number of equivalents of acid equals the number of equivalents of base; it is seen as the midpoint of a nearly vertical segment of the titration curve. The volume of titrant at the equivalence point multiplied by its concentration gives the moles of titrant species added.

Consider the Titration Curve for Aqueous Ammonia Shown Below