* Chemicals: Buffer solution, pH 7.0, 50 mL
Phenolphthalein indicator solution, 1.0 %, 1 mL
Potassium hydrogen phthalate, KHC8H4O4, 2 g
sodium hydroxide solution, NaOH, 0.1 M, 150 mL
Unknown weak acid, 1.5g
Water, distilled or deionized
* Equipment: Balance
Buret, 50 mL
Rising stand and buret clamp
Erlenmeyer flask, 125mL
Wash bottle with distilled water
Weighing dishes, 2
Part 1: Standardization of a Sodium Hydroxide Solution
1. Obtain a sample of potassium hydrogen phthalate that has been previously dried in oven and stored in a desiccator. 2. On an analytical balance, accurately weigh 0.4 g of KHP in a previously tared weighing dish. Record the precise mass in the table. 3. Transfer the KHP into an Erlenmeyer flask. Use water from a wash bottle to rinse the entire remaining solid from weighing dish to flask. 4. Add 45mL of distilled water into the flask and dissolve the KHP. 5. Obtain 75mL of NaOH solution.
6. Clean a 50mL buret and rinse it with NaOH solution.
7. Fill the buret to the above zero mark with the NaOH solution. 8. Open the stopcock to remove the air and then measure the remaining solution in the buret and record it. 9. Position the buret over the Erlenmeyer flask so the tip of buret is 2cm above the liquid. 10. Add three drops of phenolphthalein solution to the KHP solution in the flask. 11. Begin the titration by adding 1.0 mL of NaOH solution to the flask and swirl the flask to mix the content. 12. Repeat this step until 15mL of NaOH has been added to the flask. 13. Reduce the incremental volumes of NaOH to 0.5 mL until pink color persists. Reduce the rate of addition of NaOH drop by drop until the pink color starts to persist for 15 seconds. Remember to continuously swirl the flask. 14. Measure the volume of remaining NaOH in the buret. Record this volume as the...
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