Standardizing a Solution Lab

NaOH and KHP

Standardizing a Solution• Standardize means to determine a precise and accurate concentration- Normally we could mass out a desired solute to make a solution • Why can’t we do it with NaOH???- NaOH is deliquescent so we can’t trust the mass value.- Deliquescent means = tendency to absorb moisture

from the air

Deliquescent NaOH

What to do???• Standardization by Titration• Dilute then titrate against a primary standard• In this case, KHP (weak acid) can be accurately

and precisely weighed• Potassium hydrogen phthalate, simply KHP• Solid, air-stable, not hygroscopic• Molecular Mass = 204.2 g/mol

Procedure Discussion:1. Complete the prelab exercises. 2. We will complete Method 1 procedure. 3. In our procedure, a known volume of the

primary std KHP solution will be “titrated” with NaOH until a color change is noticed

4. End point is indicated by the color change5. Equivalence Point will be determined graphically

End Point = Equivalence Point

What is the End Point?

What is the Equivalence Point?• point at which an added titrant is

stoichiometrically equal to the number of moles of substance present in the sample

Strong Base NaOH

Weak Acid KHP

Conduct Procedure

Download Shared Data • Go to Wikispace, download/save 2nd Derivative

Plot for Titration 1 and Titration 2• Analyze the plot for the equivalence point • Record in mL of base, NaOH on data table

Why the derivative?

Complete the Data Analysis