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Make a Tris Buffer

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Tris is a chemical with basic properties, having a pKa of 8.1. It can be used to buffer solutions from drastic pH changes, keeping them in the pH range of 7.0 to 9.0.

Make any Tris-HCl buffer in this pH range, at any molarity using these simple steps

Difficulty: Easy
Time Required: 10 minutes

Here's How:

  1. Calculate Moles of Tris Base

    Determine the number of moles of Tris base needed by multiplying the desired molar concentration of buffer by the volume of buffer being made.

    mol/L * L = moles needed

  2. Calculate Mass of Tris Base

    Determine the mass of Tris base to weigh by multiplying the number of moles by the molecular weight (121.14 g/mol) of Tris.

    moles needed * g/mol = g

  3. Dissolve Tris Base in Water

    Dissolve the required mass of Tris into a volume of deionized water approximately 1/3 of the desired volume of buffer to be made.

  4. Adjust the pH

    Using a pH meter, titrate the solution of Tris with 1M hydrochloric acid (HCl) until the correct pH is reached.

  5. Bring to Volume

    Add the TrisHCl mixture to a volumetric flask of the desired volume and add deionized water as required to complete the solution.

Tips:

  1. Remember that pKa is not easily measured to an exact value. Slightly different pKa values might be available in the literature from different sources.

What You Need

  • Standard labware: beakers, flasks, graduated cylinders, stirbars etc.
  • pH meter and probe.
  • Stirring hotplate.
  • Tris base powder and hydrochloric acid (HCl).

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