Standardization of NaOH and Analysis of Unknown Acid Sample.

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Alex Kaplan



IB Chemistry II

Lab Report: Standardization of NaOH and

Analysis of Unknown Acid Sample


Titration is a process that involves measuring the exact volume of a solution with a known concentration and reacting the solution with a measured volume of a solution with an unknown concentration, or with a weighed sample of a solid. The solution with a known concentration is called the standard solution. To standardize sodium hydroxide (NaOH), one must first test the actual concentration of it, because NaOH is usually of questionable purity. Once the NaOH is standardized using the help of the potassium hydrogen phthalate (KHP) indicator through titration, the NaOH can then be used to determine the identity of an unknown acid sample. The indicator dye will turn pink when the solution suddenly becomes a base (indicating that enough of the titrant has been dripped into the solution to cause this reaction), and the amount of NaOH needed (hence, its concentration) will become evident. The new ‘standard solution’ will be used to then begin another process of titration, to discover the identity of H(A), the unknown acid.


The purpose of this experiment is to identify an unknown acid through the titration and standardization of a sodium hydroxide solution. When titrated using the standardized NaOH solution, the identity of the unknown acid will become evident.

Part I: The Standardization of NaOH


  • Buret and clamp
  • 5-mL pipet and safety bulb
  • 1-L glass or plastic bottle with stopper
  • 3 Erlenmeyer flasks
  • Digital scale
  • Chemical spatula
  • NaOH pellets
  • Primary standard grade potassium hydrogen phtalate (KHP)
  • Phenolphthalein indicator solution
  • Lab grip and safety goggles
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  1. Clean and rinse all glassware that will be used in the experiment. Rinse buret and pipet with distilled water.
  2. Clean and rinse the 1-L bottle and stopper. Label the bottle “0.1 M NaOH”. Put about 500mL of distilled water into the bottle.
  3. Weigh out 4g (0.1 mol) of NaOH pellets and transfer them into the 1-L bottle. Stopper and shake the bottle to dissolve the sodium hydroxide. Once the NaOH has dissolved, fill the rest of the bottle with another 500mL of distilled water.
  4. Set up the buret with the clamp and fill ...

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