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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 ??? - PowerPoint PPT Presentation
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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