Chem Pre-Lab 1

Chem Pre-Lab 1 - HCl with stirring until solution is...

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02/04/08 Determining the Equivalent Mass and Dissociation Constant of an Unknown Weak Acid by Titrometry PURPOSE: The purpose of this lab is to prepare and standardize a sodium hydroxide solution, then use titration data to determine equivalent mass and pKa of an unknown acid, then determine the acid. SAFETY: 1. Always wear safety goggles. 2. Handle glassware with care. 3. Unknown acids are corrosive, toxic, irritants, and/or hygroscopic. 4. Sodium Hydroxide is corrosive and toxic, and it can cause burns. PROCEDURE: 1. Dry and cool KHP. 2. Prepare NaOH solution. 3. Standardize NaOH solution by titrating KHP to end point. 4. Determine mass of unknown weak acide that will react with 25mL of NaOH solution. 5. Titrate unknown acide using pH meter to monitor pH. 6. Safely dispose of excess NaOH solution. PRE-LAB QUESTIONS: 1. To safely dispose of NaOH solution, transfer any remaining NaOH into discard beaker, then add 1-2 drops of phenolphthalein indicator (solutions should turn pink). Add 6M
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Unformatted text preview: HCl with stirring until solution is colorless, then discard solution down the drain. 2. a. The difference between monoprotic and diprotic acids is that monoprotic acids can only donate 1 Hydrogen proton, while diprotic acids can donate two Hydrogen protons. b. An equivalence point is when the NaOH is chemically equivalent to the acid, while the end point is when the color change to the reaction to indicating equivalency. c. Half-equivalence point is when one half of the acid is converted to the conjugate base, while an equivalence point is when the NaOH is chemically equivalent to the acid. 3. a. On separate sheet of paper b. Numb. Of Equivalents= 32.0ml NaOH*.100M NaOH= 3.2 mols NaOH c. Number Equivalents of Acid= 3.2 mols Acid d. Equivalent Mass of Acid= .653g Acid/3.2mols Acid= .204 g Acid e. pK(a)= pH= 5.29 f. K(a)= e^(-5.29)= .00504 g. Unknown Acid= Potassium Hydrogen Phthalate...
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This lab report was uploaded on 04/08/2008 for the course CHEM 202 taught by Professor Cummings during the Spring '08 term at Nevada.

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Chem Pre-Lab 1 - HCl with stirring until solution is...

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