Graphic: Wikimedia Commons User Tubifex
The ions of two compounds exchange places in an aqueous solution to form two new compounds.
AX + BY AY + BX
One of the compounds formed is usually a
precipitate (an insoluble solid), an insoluble gas that bubbles out of solution, or a molecular compound, usually water.
Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)
Pb2+(aq) + 2 NO3-(aq) + 2 K+(aq) +2 I-(aq) PbI2(s) + 2K+(aq) + 2 NO3-(aq)
Pb2+(aq) + 2 I-(aq) PbI2(s)
Double replacement (ionic) equation
Complete ionic equation shows compounds as aqueous ions
Net ionic equation eliminates the spectator ions
Lead(II) nitrate + potassium iodide lead(II) iodide + potassium nitrate
All sodium, potassium, ammonium, and nitrate salts are soluble in water. Memorization of other “solubility rules” is beyond the scope of this course and the AP Exam.
Therefore, the following slides are only for your amusement, and will not be tested
Solubility Chart: Common salts at 25C
S = Soluble
I = Insoluble
P = Partially
X = Other