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Standardizing a Solution Lab

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 ???

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Standardizing a Solution Lab

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  1. Standardizing a Solution Lab NaOH and KHP

  2. 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

  3. Deliquescent NaOH

  4. 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

  5. Procedure Discussion: • Complete the prelab exercises. • We will complete Method 1 procedure. • In our procedure, a known volume of the primary std KHP solution will be “titrated” with NaOH until a color change is noticed • End point is indicated by the color change • Equivalence Point will be determined graphically End Point = Equivalence Point

  6. What is the End Point?

  7. 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

  8. Conduct Procedure

  9. 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

  10. Why the derivative?

  11. Complete the Data Analysis

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