Exp. 9: Pre-Lab Flashcards
Exp. 9: What is the titrant for this experiment?
The titrant for this experiment is a NaOH solution that is standardized against KHP. The NaOH solution is approximately 0.1 M
Exp. 9: Is the indicator generally added to the titrant or the analyte in a titration?
The indicator is generally added to the analyte (in the receiving flask) in the titration apparatus.
Exp. 9: What is the primary standard used in this experiment (name and formula)? Define a primary standard.
The primary standard in this experiment is potassium hydrogen phthalate, KHC8H4O4 (commonly known as KHP). A primary standard is a substance that has a known high degree of purity, a relatively large molar mass, is nonhygroscopic, and reacts in a predictable way.
Exp. 9: What is the secondary standard used in this experiment (name and formula)? Define a secondary standard.
The secondary standard in this experiment is a solution of NaOH. A secondary standard is a substance/solution having a composition or concentration that has been measured relative to a primary standard. As a consequence, the concentration of NaOH is known, but it is secondary to the KHC8H4O4 (KHP).
Exp. 9: Distinguish between a stoichiometric point and an endpoint in an acid-base titration.
A stoichiometric (or equivalence) point of an acid-base titration occurs when a mix of the acid and base in a solution is in a mole ratio equal to that of the balanced equation. An endpoint in an acid-base titration occurs when the selected acid-base indicator changes color due to a slight excess of hydroxide or hydronium ion.
Exp. 9: When rinsing a buret after cleaning it with soap and water, should the rinse be dispensed through the buret tip or the top opening of the buret? Explain.
The rinse should be dispensed through the tip of the buret so that the tip has also been cleaned with the soap solution and the following rinses. (In our lab, we generally do not need soap, water is sufficient to clean a buret.)
Exp. 9: Experimental Procedure, Part A.4. In preparing the buret for titration, the final rinse is with the NaOH titrant rather than with deionized water. Explain.
The final rinse is always with the titrant so that the wall of the buret is coated with the titrant. If the final rinse were with deionized water then the titrant would be slightly diluted with the residual deionized water when filling the buret.
