Project Objectives
Standardization of NaOH (titrant) & HCl stock solutions
Preparation of 2.7 mM chlorauric acid solution
Preparation of buffer solutions
Today's Tasks
Standardization of NaOH titrant solution (trial 2)
- Using "0.2 M NaOH" stock solution as a titrant
- Using Orion 5-Star meter with pH electrode
- Meter calibrated with homemade 1:1 HAc/NaAc and 1:1 Borate buffers
- Potassium Hydrogen Phthalate (KHPth) is a primary standard for acid/base solutions
Standardization of 1 M HCl stock solution (trials 1 & 2)
- Using standardized NaOH solution as titrant
- Using Orion 5-Star meter with pH electrode
- Used 150 mL tall form beaker on stir plate with pH probe constantly in solution
Analyzed Data
Standardization of NaOH titrant
- Placed 1.023 g KHPth in 250 mL Erlenmeyer flask & added 50 mL water (grad cyl)
- After dissolution, added 5 drops phenolphthalein
- Added base in 0.05 - 5 mL increments, measuring pH at each step
- 1 drop ~ 0.05 mL; steep pH change with 1 drop at eqv pt
- End pt was 1 drop after eqv pt (Phenolthalein is ideal end pt for this standardization)
- 0.194 M NaOH
- Data file available in DropBox
Standardization of 1 M HCl stock solution
- Transferred 4 mL HCl to 150 mL tall-from beaker using volumetric pipet & added 50 mL water (grad cyl)
- Contaminated phenolthalein solution using dirty transfer pipet (yellow), so did not use
- As buret emptied, each drop shrank in size (5 drops = 0.2 mL)
- First trial significantly overshot the end point
- Note how there is an error in the calibration (8.22 pH at end point!)
- 0.948 M HCl
- Data file available in DropBox
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Project 3: Solution Preparations
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