CHAPTER 4 Reactions in Aqueous Solutions

VOCABULARY Page 94 Define all terms.

MOLARITY  Molarity = moles of solute liters of solution How to prepare a solution To prepare a solution, find the mass of the solute needed. Dissolve in a small amount of solvent. Dilute with enough solvent to make the quantity needed.

Find the volume of 12 M HCl needed to obtain 0.10 moles HCl. Volume (in liters) = moles M.10 moles HCl =.0083 L = 8.3 mL 12M What are the molarities of Al +3 and SO 4 -2 in M Al 2 (SO 4 ) 3 ? Al 2 (SO 4 ) 3(s)  2 Al +3 (aq) + 3SO 4 -2 (aq) [Al +3 ] =0.100 mole Al 2 (SO 4 ) 3 = 2 moles Al +3 x moles Al 2 (SO 4 ) 3 = M Al 2 (SO 4 ) 3 1 moleAl 2 (SO 4 ) 3 1 liter [SO 4 -2 ] = M SO 4 -2 =.200 M Al +3

MOLARITY PROBLEMS Page 95 2, 4, 6, 8

SOLUBILITY RULES 1. Salts containing Group I elements are soluble (Li +, Na +, K +, Cs +, Rb + ). Exceptions to this rule are rare. Salts containing the ammonium ion (NH 4 + ) are also soluble. 2. Salts containing nitrate ion (NO 3 - ) are generally soluble. 3. Salts containing Cl -, Br -, I - are generally soluble. Important exceptions to this rule are halide salts of Ag +, Pb 2+, and (Hg 2 ) 2+. Thus, AgCl, PbBr 2, and Hg 2 Cl 2 are all insoluble. 4. Most silver salts are insoluble. AgNO 3 and Ag(C 2 H 3 O 2 ) are common soluble salts of silver; virtually anything else is insoluble.

5. Most sulfate salts are soluble. Important exceptions to this rule include BaSO 4, PbSO 4, Ag 2 SO 4 and SrSO Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble. Hydroxide salts of Group II elements (Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of transition metals and Al 3+ are insoluble. Thus, Fe(OH) 3, Al(OH) 3, Co(OH) 2 are not soluble. 7. Most sulfides of transition metals are highly insoluble. Thus, CdS, FeS, ZnS, Ag 2 S are all insoluble. Arsenic, antimony, bismuth, and lead sulfides are also insoluble. 8. Carbonates are frequently insoluble. Group II carbonates (Ca, Sr, and Ba) are insoluble. Some other insoluble carbonates include FeCO 3 and PbCO 3.

9. Chromates are frequently insoluble. Examples: PbCrO 4, BaCrO Phosphates are frequently insoluble. Examples: Ca 3 (PO 4 ) 2, Ag 3 PO Fluorides are frequently insoluble. Examples: BaF 2, MgF 2 PbF 2.

PRECIPITATION REACTIONS Page , 12, 14-25

#14 Name the reagent, if any, that you would add to a solution of cobalt(III)chloride to precipitate a)Cobalt(III) phosphate add sodium phosphate b)Cobalt (III) carbonate add sodium carbonate c)Cobalt(III) hydroxide add sodium hydroxide