U2 S3 L2 Titration page 603: Acid-Base Titration pages : Titration Step by Step page 838: Precision, Error and Accuracy Questions page 616: items 3 and 5 Lab #3. p 606

Upon completion of this lesson, you should be able to: describe the process of a titration define primary standard and recognize its importance in a titration procedure define standardized solution distinguish between indicator endpoint and equivalence point state the importance of conducting several trials of an experiment in order to minimize random error

Definitions Titration is the progressive addition of one reagent to another. –In acid-base chemistry, the reagents are aqueous solutions, one of which is either a strong acid or a strong base. A typical titration involves progressively adding a solution of known concentration (the titrant) from a buret to a solution of unknown concentration (the sample) in a container below the buret. The amount of titrant added is just enough to completely neutralize the sample. An indicator is usually added to the sample to detect the equivalence point. –The point at which chemically equivalent amounts of titrant and sample have reacted.

Standards A standardized solution is one whose concentration is determined from data collected by titration. –HCl has to be standardized because it is a gas at room temperature. It is difficult to dissolve precise amounts of any gas in water. Moreover, once dissolved, tiny amounts of HCl have the tendency to escape from solution thereby reducing the concentration of dissolved HCl. –NaOH is a deliquescent or hygroscopic solid - it absorbs moisture from the air. That is, when you weigh out a sample of NaOH, you are obtaining the mass of NaOH plus the mass of the water it has absorbed from the air. If you prepare a solution using the measured mass of NaOH, its molar concentration will be slightly lower than expected because of the absorbed moisture. A primary standard or a solution that can be prepared from a pure form of the solute to a precise molar concentration. –Acids like HCl are standardized using a primary standard such as sodium carbonate (Na 2 CO 3 ) –bases like NaOH and KOH are standardized using potassium hydrogen sulfate (KHSO 4 ) or potassium hydrogen phthalate (KHC 8 H 4 O 4 ).

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