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Technical data


Absorption spectra and pKa values of p-methoxyphenol

Article no: P3070467
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Principle

For weak acids HA, the position of the Ka and pKa values that characterise the dissociation equilibrium in the ground state can be determined from photometric measurements in solutions having different pH values. Further to this, the pKa* value for the excited state is accessible from the spectrophotometric data.

Benefits

  • Modern spectrophotometer with display
  • Spectrophotometer can be used for many other applications
  • Detailed operating instructions

Tasks

  1. Record near UV absorption spectra of p-methoxyphenol in dilute HCl, NaOH and 5 different borate buffer solutions of known pH.
  2. Calculate the pKa and pKa* values for the system.

Learning objectives

  • Ground and excitation states of molecules
  • Electron excitation spectroscopy (UV-VIS spectroscopy)
  • Spectroscopical energy and adsorption measurement
  • Jablonski diagram and Foerster cycle
  • pKa and pKa* values
  • Henderson-Hasselbalch equation
  • Van't Hoff's reaction isotherms
  • Gibbs-Helmholtz equation
  • Lambert-Beer law
  • Photometry

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