User:Douglas M. Fox/Notebook/AU CHEM-571 F2011 Lab Support/2012/01/27

From OpenWetWare

Jump to: navigation, search
Project 3: Solution Preparations Main project page
Previous entry      Next entry

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





Personal tools