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Predicting Reactions General Rules

1. All reactions occur. Predicting Reactions General Rules. 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

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Predicting Reactions General Rules

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  1. 1. All reactions occur Predicting ReactionsGeneral Rules 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

  2. 6. “Burned in air” - means combustion in O2 Predicting ReactionsGeneral Rules (Pg 2) 7. “Heated” means decomposition 2

  3. PredictingReactionsMajor 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

  4. Predicting Reactions A. Must put them together. Need sensible oxidation # B. Example : Solid sulfur is burned in oxygen S + O2 => SO2 1. Looking for two uncombined elements (Syn) C. Example : A piece of solid zinc is heated in chlorine gas Zn + Cl2 => ZnCl2 4

  5. Predicting Reactions A. Only can break up into two or more product B. Usually produces simple oxide and oxide gases 2. Look for single reactant (Analysis) C. Example: Solid calcium carbonate is heated. CaCO3 => CaO + CO2 5

  6. Predicting Reactions A. “Burned in air or oxygen is same 3. Look for Combustion Reactions B. Always forms oxide gases I. C - CO or CO2 II. H - H2O III. S - SO2 or SO3 C. Example : Propane is burned in air C3H8 + O2 => CO2 + H2O D. Example : Carbon disulfide is burned in air CS2 + O2 => CO2 + SO2 6

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

  8. B. Acid/Base with salt of other Predicting Reaction Remember : Hydrolysis (salts breaking up into ions) Same as simple acid-base reaction Example: Sol’n of hydrochloric acid & sodium bicarbonate is mixed 4. Looking for Acid-Base Reaction (Cont’d) H+ + HCO31- => H2CO3 Example : Sol’n of potassium hydroxide & ammonium chloride mix. OH- + NH3 + H2O NH41+ => 8

  9. C. Polyprotic acid & Sulfuric acid Polyprotic : Only one H+ comes off or on Exception: “Excess acid”- goes all the way Predicting Reaction Sulfuric acid - For now, assume both concentrated & dilute form completely dissociate 4. Looking for Acid-Base Reaction (Cont’d) Example: “Equal volume” of “equimolar” solutions of phosphoric acid & potassium hydroxide are mixed H3PO4 + OH1- => H2PO41- + H2O Example : Excess hydrochloric acid mixed w/sol’n potassium sulfide H+ + S2- => H2S 9

  10. A. General Assumptions (Does not replace solubility rules) Predicting Reaction 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) 5. Looking for Two Salt Solution Example: A sol’n of silver nitrate is added to potassium iodide sol’n Ag+ + I1- => AgI (Remember reaction must occur) 10

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