Volumetric Analysis

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Volumetric Analysis

• Titrations

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Titrations
Measures the amount of analyte that quantitative
reacts with titrant Reaction must
be Fast Complete Possess Known Stoichiometry
D. C. Harris, Quantitative Chemical Analysis, 6th
Ed. P 130
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Titration Types

• By Reaction Type
• Acid/Base
• Complexometric
• Precipitation
• Redox

• By Indicator
• Spectrophotometric
• Electrochemical
• pH

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Titration Calculations

• A 0.8345 g sample of potassium hydrogen phthalate
  required 38.31 mL of 0.1023 M NaOH to reach the
  endpoint. What is the concentration (M) of NaOH?
• A 10.00 mL sample of an HCl solution to be used
  as an acid standard required 28.45 mL of the
  previously standardized NaOH to reach the
  endpoint. What is the concentration of the HCl
  solution?

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Molecular Weight Determination

• A 0.1046 g diprotic organic acid acid required
  23.47 mL of 0.1072 M standard KOH to reach the
  first endpoint. What is the molecular weight of
  the acid?

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Back Titration

• The concentration of Manganese in a water sample
  was measured using an EDTA back titration. Find
  the concentration of manganese if a 50.00 mL
  water sample was treated with 10.00 mL of 0.02041
  M EDTA and required 3.21 mL of 0.00934 M Zn to
  reach the endpoint.

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Standardization

• Primary Standards
• high purity
• air stability
• absence of hydrate water
• modest cost
• soluble
• large formula weight/mole
• secondary standard with demonstrated assay can
  be used!

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A note about Reagents
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Keeping Analytical Reagents Pure

• Keep spatulas out! Pour from bottle to beaker or
  flask
• Never return reagents to the original container
• Replace caps immediately
• Do not place stoppers on benchtops
• Store chemicals in a cool, dry, dark place

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Standard Solutions

• stable, no change in concentration
• react rapidly w/ analyte
• react completely w/ analyte
• react w/ known stoichiometry

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Titration Curves
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End Points Indicators