Net Ionic Equations Sec. 4.2 Precipitation Reactions
Download
Report
Transcript Net Ionic Equations Sec. 4.2 Precipitation Reactions
Sec. 4.2 Precipitation Reactions
1
A precipitation reaction occurs when two ionic
compounds react together to form a soluble and an
insoluble product
Precipitation rxns are also called double replacement
reactions
◦ AC + BD AD + BC where one product is a ppt.
Products can be predicted using Solubility Rules
2
See Table 4.1 Solubility Guidelines For
common Ionic Compounds in Water
3
Example: Aqueous solutions of silver nitrate
and sodium chloride are mixed together
AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)
AgCl (s) is the ppt since “all chlorides are soluble
except Ag+, Hg22+, and Pb2+”
4
Example: Aqueous solutions of potassium
hydroxide and iron (III) iodide are mixed.
3KOH (aq) + FeI3 (aq) 3KI (aq) + Fe(OH)3 (s)
Fe(OH)3 (s) is the ppt since “all hydroxides are
insoluble except Ca2+, Sr2+, and Ba2+
5
Ionic Equations– chemical equations that show
the soluble reactants/products as ions
◦ Ex: AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)
Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq)
AgCl(s) + Na+(aq) + NO3- (aq)
Ex: 3KOH (aq) + FeI3 (aq) 3KI (aq) + Fe(OH)3 (s)
3K+(aq) + 3OH-(aq) + Fe3+(aq) + 3I-(aq)
3K+(aq) +3I- (aq) + Fe(OH)3 (s)
6
Net Ionic Equations (NIE’s) – chemical equations
that show only the ions responsible for the
precipitate
The soluble ions are called spectator ions
◦ AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)
◦ Ag+ (aq) + NO3- (aq) + Na+ (aq) + Cl- (aq)
AgCl (s) + Na+ (aq) + NO3- (aq)
◦ NIE: Ag+ (aq) + Cl- (aq) AgCl (s)
7
•
•
Ex: 3KOH (aq) + FeI3 (aq) 3KI (aq) + Fe(OH)3 (s)
3K+(aq) + 3OH-(aq) + Fe3+(aq) + 3I-(aq)
3K+(aq) + 3I- (aq) + Fe(OH)3 (s)
• 3K+(aq) + 3OH-(aq) + Fe3+(aq) + 3I-(aq)
3K+(aq) +3I- (aq) + Fe(OH)3 (s)
•
NIE: 3OH-(aq) + Fe3+(aq) Fe(OH)3 (s)
8
You try it:
◦ Write the net ionic equation for the following reaction:
Aqueous solutions of manganese (IV) acetate and lithium
phosphate are reacted together
3Mn(C2H3O2)4 (aq) + 4Li3PO4 (aq)
Mn3(PO4)4 (s) + 12LiC2H3O2 (aq)
3Mn4+ (aq) + 4C2H3O2- (aq) + 12Li+ (aq) + 4PO43- (aq)
Mn3(PO4)4 (s) + 12Li+ (aq) + C2H3O2- (aq)
NIE: 3Mn4+ (aq) + 4PO43- (aq) Mn3(PO4)4 (s)
9
Guidelines to writing net ionic equations (NIE’s)
Identify the reaction type based on the given reactants
Write the balanced molecular equation for the reaction
Rewrite the equation to show the ions that form in
solution when each soluble strong electrolyte breaks up
into its component ions
Soluble strong electrolytes: soluble ionic compounds, strong
acids, strong bases
Leave elements, molecular compounds, weak and nonelectrolytes, solids, liquids, and gases in their original
form (no ions)
Soluble weak electrolytes: soluble molecular compounds,
weak acids, weak bases
Identify and cancel spectator ions that occur on both
sides of the equation
10