# Predicting solubility - PowerPoint PPT Presentation

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Predicting solubility. Using the table of solubilities we can now predict which of the products of a double replacement reaction will be insoluble ( form solids or precipitates : have low solubilities) and which will remain soluble. Pb(NO 3 ) 2 (aq) + 2 KI(aq)  PbI 2 (s) + 2KNO 3 (aq).

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Predicting solubility

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## Predicting solubility

• Using the table of solubilities we can now predict which of the products of a double replacement reaction will be insoluble (form solids or precipitates : have low solubilities) and which will remain soluble.

### Pb(NO3)2(aq) + 2 KI(aq)  PbI2 (s) + 2KNO3(aq)

• overall ionic equation, which separates all the ions out:

Pb2+(aq) + 2 NO3- (aq) + 2 K- (aq) + 2 I- (aq)  PbI2 (s) + 2 K+ (aq) + 2 NO3- (aq)

Pb2+ (aq) + 2 I- (aq)  PbI2 (s)

Stays as a solid

• The NO3- ion and the K+ ion are called spectator ions.

• Silver nitrate combines with potassium iodide.

• a) Nonionic or double replacement reaction

AgNO3 (aq)+KI (aq) → AgI (?)+KNO3 (?)

• Using the solubility table we see that nitrates are soluble with all positive ions and Iodide ion is insoluble with silver.

AgNO3 (aq)+KI (aq)→AgI (s)+KNO3 (aq)

• Now that we have predicted the solid that will form we can proceed to write the net ionic equation.

• Ag + (aq) + I- (aq) → AgI (s)

• silver nitrate + potassium iodide

• ammonium sulfide + lead(II) nitrate

• zinc nitrate + sodium carbonate

### Separating ions:Pb 2+ (aq) ; Ba 2+ (aq) ; Cu 2+ (aq)

Ba2+ and Cu2+

soluble

PbCl2 ppt outs

CuS ppt out

Ba2+ soluble

Ba3 (PO4)2 ppt out

• Using the solubility table create a flow chart that describes how to separate the following ions, if they are dissolved together in a solution. The last ion may remain in solution.

• a) Ag+ (aq) ; Ba2+ (aq) ; Mg2+ (aq)

• b) Ba2+ (aq) ; K+ (aq) ; Zn2+ (aq)

• c) Pb2+ (aq) ; Al3+ (aq) ; Sr2+ (aq)

• d) Sr2+ (aq) ; Mg2+ (aq) ; Fe3+ (aq)

1. Ionic Substances ( containing a metal or NH4- ion )

• Ionic substances are composed of positive and negative ions. Arrhenius proposed that ionic substances come apart when they enter a water solution, and the ions are free to move about in the solution. The called this process dissociation.

• CaCl2 (s) -------> Ca 2+ (aq) + 2 Cl- (aq)

• * Notice that the reactions are balanced for charge and # of atoms.

2. Acids (containing nonmetals with hydrogen written first in the formula)

• Certain molecular substances also form mobile ions when placed in solution. Arrhenius proposed that acids when placed in solution form mobile ions. He called this process ionization.

• H2 SO4 (l) -------> 2 H+ (aq) + SO4 2- (aq)

• In both cases (dissociation and ionization) the end result is mobile ions in solution. Thus since ions are present and can move, both acids and ionic substances conduct electricity in solution and are termed electrolytes.

3. Molecular (contain only nonmetals)

• Molecular substance that are not acids on the other hand do not ionize nor dissociation and do not form ions in solution. Therefore these substances are non-electrolytes.

• CO2 (g) ------> CO2 (aq)