Indicators and Buffer Solutions

  1. What does this equation represent?
    HIn(aq) + H2O(l) ↔ H3O+(aq) + In-(aq)
    The dissociation of indicators (which are weak acids)
  2. What does this equation represent?
    KIn = [H3O+][In-] / [HIn]
    The dissociation constant for indicators
  3. In aqueous solution the colour of the acid is distinctly different from that of its...?
    conjugate base
  4. What is the colour of the indicator determined by?
    The ratio of [HIn] to [In-]
  5. The theoretical point at which the colour changes occurs when...?
    [H+] = KIn
  6. The colour change is assumed to be distinguishable when [HIn] and [In-] differ by a factor of...?
  7. What expression is used to estimate the pH change over which a colour change occurs?
    pH = pKIn ± 1
  8. What is a buffer solution?
    A buffer solution is one in which the pH remains approximately constant when small amounts of acid or base are added
  9. What does an acid buffer consist of?
    A solution of a weak acid and one of its salts
  10. Explain how an acid buffer solution works
    In an acid buffer solution the weak acid can supply hydrogen ions when these are removed by the addition of a small amount of base.  The salt of the weak acid provides the conjugate base, which can absorb excess hydrogen ions produced by the addition of a small amount of acid.
  11. What does a basic buffer solution consist of?
    A weak base and one of its salts
  12. Explain how a basic buffer solution works
    In a basic buffer solution the weak base removes hydrogen ions and the conjugate acid provided by the salt supplies hydrogen ions when these are removed.
  13. How can the pH of an acid buffer solution be calculated?
    pH = pKa - log [acid] / [salt]
  14. What do you need to calculate the required compositions of an acid buffer solution?
    The desired pH and the acid dissociation constant (pKa)
Card Set
Indicators and Buffer Solutions
Advanced Higher Chemistry - Unit Two - Indicators and Buffer Solutions