Predicting Reactions General Rules 1. All reactions occur 2. Net ionic reactions only 3. Phases are not required : aqueous by charge 4. Completely dissociated chemicals shown as ions (i.e. strong acid is H+ & A-) 5. All other dissociated chemicals shown as complete compound (i.e. weak acid is HA) 1

Predicting Reactions General Rules (Pg 2) 6. “Burned in air” - means combustion in O 2 7. “Heated” means decomposition 2

Predicting Reactions Major Types 1.Look for two uncombined elements (Syn.) 2.Look for single reactant (Decomposition) 3.Look for Combustion Reaction 4.Look for Acid-Base Reactions (DR) 5.Look for Two Salt Solution (Precip) 6.Look for REDOX Reaction 7.Look for water as Reactant 8.Look for Transitional metal and Ligands 3

Predicting Reactions 1. Looking for two uncombined elements (Syn) 4 A.Must put them together. Need sensible oxidation # B.Example : Solid sulfur is burned in oxygen S + O 2 => SO 2 C.Example : A piece of solid zinc is heated in chlorine gas Zn + Cl 2 =>ZnCl 2

Predicting Reactions 2.Look for single reactant (Analysis) 5 A. Only can break up into two or more product B. Usually produces simple oxide and oxide gases C. Example: Solid calcium carbonate is heated. CaCO 3 => CaO +CO 2

Predicting Reactions 3.Look for Combustion Reactions A.“Burned in air or oxygen is same B.Always forms oxide gases I.C - CO or CO 2 II.H - H 2 O III.S - SO 2 or SO 3 C.Example : Propane is burned in air C 3 H 8 + O 2 =>CO 2 + H 2 O D.Example : Carbon disulfide is burned in air CS 2 + O 2 =>CO SO 2

Predicting Reaction 4. Looking for Acid-Base Reaction A. Acid and Base Be careful : only strong acid & strong base give H+ + OH- => H2O Weak acid/base : can’t get rid of other part Example: Solution of hydrofluoric acid & sodium hydroxide are mixed HF +OH- =>F- +H2OH2O (must keep F- ) 7

Predicting Reaction 4. Looking for Acid-Base Reaction (Cont’d) B. Acid/Base with salt of other Remember : Hydrolysis (salts breaking up into ions) Same as simple acid-base reaction Example: Sol’n of hydrochloric acid & sodium bicarbonate is mixed H+ +HCO 3 1- =>H 2 CO 3 8 Example : Sol’n of potassium hydroxide & ammonium chloride mix. OH- + NH 4 1+ => NH 3 + H 2 O

Predicting Reaction 4. Looking for Acid-Base Reaction (Cont’d) C. Polyprotic acid & Sulfuric acid Polyprotic : Only one H+ comes off or on Exception: “Excess acid”- goes all the way Sulfuric acid - For now, assume both concentrated & dilute form completely dissociate Example: “Equal volume” of “equimolar” solutions of phosphoric acid & potassium hydroxide are mixed H 3 PO 4 +OH 1- =>H 2 PO H 2 O 9 Example : Excess hydrochloric acid mixed w/sol’n potassium sulfide H+ +S 2- =>H2SH2S

Predicting Reaction 5. Looking for Two Salt Solution A. General Assumptions (Does not replace solubility rules) I. A salt containing (1- charge) anion is SOLUBLE (don’t forget solubility rules especially AgCl) II. A salt containing (2- or 3- charge) anion : INSOLUBLE (don’t forget solubility rules especially with sulfate) Example: A sol’n of silver nitrate is added to potassium iodide sol’n Ag + +I 1- =>AgI (Remember reaction must occur) 10