Question

Explain how to use potassium hydrogen phthalate to standardize a solution of NaOH.

Short answer

The standardization of NaOH solution in the burette is performed (titration) with the help of potassium hydrogen phthalate in the Erlenmeyer flask with a sufficient amount of distilled water and three to four drops of phenolphthalein indicator.

Step-by-step solution

Definition of Standardization.

Standardization is the phenomenon of determining the exact concentration of the solution that is going to be used in the further titration process.

A solution is standardized using a solution of known concentration of another compound namely the primary standard. The standardized solution is therefore helpful to determine the concentration of a completely unknown given solution.

The procedure of using potassium hydrogen phthalate to standardize a solution of NaOH.

• Firstly, the Potassium hydrogen phthalate (KHP) is dried at ${105}^{°}\mathrm{c}$before weighing.

• The dried compound is weighed carefully and accurately in a balance and poured into the Erlenmeyer flask.

• A sufficient amount of distilled water is added and the quantity of KHP and distilled water used is noted down.

• Some quantity of NaOH solution that is about to standardize is taken and the burette is rinsed several times with the$\mathrm{NaOH}$solution.

• Now, the burette is filled with NaOH solution appropriately.

• Three to four drops of phenolphthalein indicator are added into the Erlenmeyer flask containing KHP solution and then stirred gently with mechanical shaking.

• The Erlenmeyer flask containing KHP solution is placed below the burette and titrated with NaOH solution in the burette.

• The volume of NaOH solution at the endpoint is noted.

• Theendpointis the appearance ofpale permanent pink color in this case.

• The steps are repeated two to three times and the concordant value is recorded.

• Knowing the volume of NaOH solution at the endpoint and the volume and strength of KHP solution used, the actual strength of NaOH solution can be calculated.