SCH3U
Ionic Equations
Double displacement reactions can take place in two forms when in solution. These are ____________
reactions and _____________________reactions.
Precipitation reactions occur when two solutions are added and a precipitate (solid) will form. A
_____________ is a salt that does not dissolve in water.
AgNO3(aq) + NaCl(aq)  NaNO3(aq) + AgCl(s)
In this reaction, sodium started as a cation and ended as a cation. It stayed in solution. What other
ion did? _____
The only reaction to take place was a silver cation combining with a chloride anion to form silver
chloride.
Ionic Equation
Ag1+(aq) + NO31-(aq) + Na1+(aq) + Cl1-(aq)  Na1+(aq) + NO31-(aq) + AgCl(s)
Net Ionic Equation
Ag1+(aq) + Cl-1(aq)  AgCl(s)
Spectator Ions
Na+1 and NO3-1
Spectator ions do not take place in the reaction but are present during the reaction.
If two solutions are mixed and no precipitation occurs, it is not considered a chemical reaction
unless there is evidence of a chemical reaction.
Ex. NaCl(aq) + KBr(aq)  ___________
Net ionic equations of reactions that do not precipitate:
2H+(aq) + CO32-(aq)  ____________________
NH4+ + OH1-(aq)  _____________________
H+(aq) + OH-(aq)  ______________________
– gas formation
– odour formation
– heat formation
Double displacement reactions can also result in the formation of a gas (carbon dioxide, and ammonia).
They also occur when an acid reacts with a base and water is produced.
HCl(aq) +
Acid
+
NaOH(aq)
Base


________
Salt
+
+
___________
water
A qualitative technique used to detect ions is a flame test. A dissolved cation placed in a flame will give
off a distinctive colour.
Fig. 6 p.439 outlines colours for flame tests of aqueous cations.