Spectator ion
Template:Short description A spectator ion is an ion that exists both as a reactant and a product in a chemical equation of an aqueous solution.[1]
For example, in the reaction of aqueous solutions of sodium carbonate and copper(II) sulfate:
- 2 Page Module:Chem2/styles.css has no content.Na+(aq) + Page Module:Chem2/styles.css has no content.CO2−3(aq) + Page Module:Chem2/styles.css has no content.Cu2+(aq) + Page Module:Chem2/styles.css has no content.SO2−4(aq) → 2 Page Module:Chem2/styles.css has no content.Na+(aq) + Page Module:Chem2/styles.css has no content.SO2−4(aq) + Page Module:Chem2/styles.css has no content.CuCO3(s)
The Page Module:Chem2/styles.css has no content.Na+ and Page Module:Chem2/styles.css has no content.SO2−4 ions are spectator ions since they remain unchanged on both sides of the equation. They simply "watch" the other ions react and does not participate in any reaction, hence the name.[1] They are present in total ionic equations to balance the charges of the ions. Whereas the Page Module:Chem2/styles.css has no content.Cu2+ and Page Module:Chem2/styles.css has no content.CO2−3 ions combine to form a precipitate of solid Page Module:Chem2/styles.css has no content.CuCO3. In reaction stoichiometry, spectator ions are removed from a complete ionic equation to form a net ionic equation. For the above example this yields:
So: 2 Page Module:Chem2/styles.css has no content.Na+(aq) + Page Module:Chem2/styles.css has no content.CO2−3(aq) + Page Module:Chem2/styles.css has no content.Cu2+(aq) + Page Module:Chem2/styles.css has no content.SO2−4(aq) → 2 Page Module:Chem2/styles.css has no content.Na+(aq) + Page Module:Chem2/styles.css has no content.SO2−4(aq) + Page Module:Chem2/styles.css has no content.CuCO3(s) (where x = spectator ion)
- ⇒ Page Module:Chem2/styles.css has no content.CO2−3(aq) + Page Module:Chem2/styles.css has no content.Cu2+(aq) → Page Module:Chem2/styles.css has no content.CuCO3(s)
Spectator ion concentration only affects the Debye length. In contrast, potential determining ions, whose concentrations affect surface potential (by surface chemical reactions) as well the Debye length.
Net ionic equation
A net ionic equation ignores the spectator ions that were part of the original equation.[1] So, the net ionic equation only shows the ions which reacted to produce a precipitate.[1] Therefore, the total ionic reaction is different from the net reaction.
See also
References
Page Template:Reflist/styles.css has no content.
- ^ a b c d Page Module:Citation/CS1/styles.css has no content.Mustoe, Frank (May 22, 2001). Chemistry 11 (Textbook) (1st ed.). McGraw-Hill Ryerson School. Chapter 9.1. ISBN 978-0070886810.
