# Lecture 72/1/06. Precipitation reactions What are they? Solubility?

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Lecture 72/1/06

Precipitation reactions What are they? Solubility?

Solubility Rules Soluble CompoundsExceptions NO 3 - None C 2 H 3 O 2 - (acetate)None Cl -, Br -, I - Compounds with Ag +, Hg 2 2+, Pb 2+ SO 4 2- Compounds with Sr 2+, Ba 2+, Hg 2 2+, Pb 2+ Group 1A and NH 4 + None Insoluble CompoundsExceptions S 2- Group 1A and NH 4 + [Ca 2+, Sr 2+, Ba 2+ ] CO 3 2-,PO 4 3-, C 2 O 4 2-, CrO 4 2- Group 1A and NH 4 + OH - Group 1A and NH 4 + [Ca 2+, Sr 2+, Ba 2+ ]

Equations Pb(NO 3 ) 2 reacts with NaI (aq) to form the insoluble compound, PbI 2. Molecular Equation? Complete Ionic Equation? Net Ionic Equation?

Solubility vs. Solubility constant (K sp ) What is the difference? BaSO 4 (s) ⇄ Ba 2+ (aq) + SO 4 2- (aq) Ba 2+ (aq) + SO 4 2- (aq) ⇄ BaSO 4 (s)

What is the K sp for AgI if the solubility equals 9.2 x 10 -9 M at 25˚ C?

The K sp of AgBr at 100 ˚C is 5 x 10 -10. Calculate the solubility of AgBr at that temperature in molarity.

A saturated solution of silver oxalate (Ag 2 C 2 O 4 ) contains 6.9 x 10 -5 M of C 2 O 4 2- at 25˚C. Calculate the K sp of silver oxalate at that temperature.

The K sp of MgF 2 = 5.2 x 10 -11. Calculate the solubility in molarity and grams per liter.

Comparison of solubility based on K sp AgI (K sp = 8.5 x 10 -17 ) < AgBr (K sp = 5.4 x 10 -13 ) < AgCl (K sp = 1.8 x 10 -10 ) PbI 2 (K sp = 9.8 x 10 -9 ) < PbBr 2 (K sp = 6.6 x 10 -6 ) < PbCl 2 (K sp = 1.7 x 10 -5 ) Can only compare salts with same ion ratio AgCl (K sp = 1.8 x 10 -10 ) vs. Ag 2 CO 3 (K sp = 8.5 x 10 -12 ) Solubility of AgCl = 1.3 x 10 -5 mol/L Solubility of Ag 2 CO 3 = 1.3 x 10 -4 mol/L