Buffer Calculations

Key Questions

  • Why are buffer solutions used to calibrate pH?

    Buffer solutions are used to calibrate pH meters because they resist changes in pH.

    When you use a pH meter to measure pH, you want to be sure that if the meter says pH = 7.00, the pH really is 7.00.

    www.all-about-ph.com

    So you use solutions of known pH and adjust the meter to display those values.

    Buffers are ideal for this purpose because:

    • They are easily prepared for a given pH.
    • They are stable for long periods of time.
    • They resist changes in pH if you accidentally add a little acid or base or even water.

    www.extension.org

    Ernest Z. · 13 · Apr 25 2015
  • How do you calculate buffer capacity?

    A buffer solution will maintain a constant pH with the addition of small amounts of acid and alkali.

    There is a limit to the amount of acid or alkali that the buffer can handle.

    The buffer capacity is given by the expression:

    (dn)/(d(pH))

    dn is a tiny amount of added base which results in tiny change in pH shown as d(pH)

    If you have a weak acid whose dissociation constant is K_a then the buffer capacity is given by :

    upload.wikimedia.org (From Wiki)

    C_A is the concentration of the acid.

    Michael · 1 · Dec 7 2014

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