Chem 23

• Spectator ions are ions that do not participate in the reaction and do not affect the equilibrium of the system
• Net ionic equation is the summarized reaction including ions that participated in the reaction (the spectator ions were omitted).
• The equilibrium constant for a system involving a slightly soluble salt and its corresponding ions in a saturated solution is the solubility product constant (Ksp).
• Molar solubility or the solubility of a salt is expressed as the concentration of the “dissolved solid” in a saturated solution
• Ions present in mixtures may be specifically precipitated by titrating a specific solution that reacts with the ion and forming an insoluble product. These chemical reactions can be used to stoichiometrically determine the amount of unknown ions in a solution.
• Silver is an ion that is very sensitive and almost always forms precipitate. That is why chemists take advantage of this property and use silver as titrants in argentometric titrations. Examples of this argentometric titrations are the Volhard Method, Mohr Method, and Fajans Method.
• Mohr method

  The first type of indicator is a species that forms a precipitate with the titrant.

  Titration’s end point = titrand’s end point – reagent blank’s end point
• Volhard method uses a species that forms a colored complex with the titrant or the titrand.

  Amount of silver precipitated with chloride = original silver content - the excess silver
• Fajans method

  The third type of end point uses a species that changes color when it adsorbs to the precipitate.