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SUMMARY OF CHEMICAL REACTIONS I) Synthesis reactions A + X -------------> AX a. Metals react with non-metals to produce binary salts (two elements, no polyatomic) b. Metal oxides (basic anhydrides) react with water to yield bases (metal hydroxides) c. Non-metal oxides (acid anhydrides) react with water to yield acids (oxidation number of non-metal does not change – do an imaginary charge check!) d. Metal oxides react with non-metal oxides to produce a polyatomic salt (Oxidation number of non-metal does not change – do an imaginary charge check!) II) Decomposition reactions AX -------------> A + X a. Acids with oxygen decompose to give non-metal oxides and water Acids with oxygen decompose to give non-metal oxides and water (oxidation number of non-metal does not change – do an imaginary charge check! b. Metallic hydroxides, or bases, decompose to give metal oxides and water c. Metallic carbonates decompose to give metal oxides and carbon dioxide d. Metallic chlorates decompose to give metal chlorides and oxygen e. Metallic nitrates decompose to give metal nitrites and oxygen f. Ammonium carbonate decomposes to give ammonia, water, and CO2 g. Sulfurous acid decompose to give water and sulfur dioxide h. Carbonic acid decomposes to give water and carbon dioxide i. Ammonium hydroxide decomposes to give ammonia and water j. Binary compounds decompose to give two elements (with energy) k. Hydrogen peroxide decomposes to give water and oxygen l. Polyatomic salts not listed above can decompose to form the metal oxide and non-metal oxide that formed them (oxidation number of non-metal does not change – do an imaginary charge check!) III) Single Replacement reactions A + BX -------------> AX + B a. b. c. d. Active metals replace less active metals in ionic compounds in aqueous solutions Active metals replace H in water to form metal hydroxides (bases) and H2 Active metals replace H in acids to form hydrogen gas and a salt Active non-metals replace less active non-metals in ionic compounds in aqueous solutions e. Non-aqueous replacement reactions – reductions of metal oxides by hydrogen or other gases: - H2 + CuO → Cu + H2O (occur at high temperatures!) - CO + Fe2O3 → Fe + CO2 IV) Metathesis (Double Replacement reactions) – Removal of ions is the driving force (cations change partners) to form a solid, liquid, or gas that stays whole as a molecule – involves two ionic compounds! AX + BY -------------> AY + BX ONE OF YOUR PRODUCTS MUST BE FORMED AS A SOLID, LIQUID, OR GAS – THIS IS WHAT DRIVES A DOUBLE REPLACEMENT REACTION! a. Formation of a precipitate (solid) governed by the solubility rules b. Formation of a gas - Common gases are H2S, CO2, SO2, NH3 1. 2. 3. 4. - Any sulfide (S-2) plus any acid forms H2S gas and a salt Any carbonate (CO3-2) plus any acid forms CO2, HOH, and a salt Any sulfite (SO3-2) plus any acid forms SO2, HOH, and a salt Any ammonium (NH4+1) compound plus a soluble hydroxide form NH3, HOH, and a salt IMPORTANT – IF YOU CREATE NH4OH, H2CO3, AND H2SO3, THEY WILL IMMEDIATELY BREAK DOWN INTO H2O AND A GAS – NH3, CO2, OR SO2 - THESE THREE COMPOUNDS ARE UNSTABLE AND CANNOT BE ISOLATED! c. Formation of a molecule – which is a compound that does not dissociate well in water, due to its covalent nature! It stays together as a molecule! Example – H2O! - Acid-base neutralization is one type – ACID PLUS BASE = WATER PLUS SALT d. Hydrolysis – Reverse of an acid-base neutralization – a salt reacts with water – this will only happen with one in a trillion water molecules! - - One in a trillion water molecules can break apart into H+1 and OH-1 The salt then breaks apart, and a double replacement reaction occurs, with the salt reacting with the H+1 and the OH-1 Produces an acid and a base every time! Salts are products of neutralization, but salts that undergo hydrolysis are not neutral! 1. Salts of a strong acid and a weak base + H2O give an acidic solution 2. Salts of a weak acid and a strong base + H2O give a basic solution 3. Salts of a strong acid and a strong base do not undergo hydrolysis – their solutions are neutral! 4. Salts of a weak acid and a weak base + H2O may give an acidic, basic, or neutral solution – look at the strength of the acid or base produced (Ka or Kb) A COUPLE OF REMINDERS FOR REACTIONS THAT OCCUR IN WATER, WHEN YOU GO TO WRITE IONIC REACTIONS: i. ii. iii. iv. Strong acids ionize or dissociate 100% in water Strong bases ionize or dissociate 100% in water Most common (soluble) salts dissociate in water Weak acids and water do not dissolve well in water, and should be written as whole molecules! STRONG ACIDS: HClO4 HClO3 HCl HBr KOH Ca(OH)2 HI HNO3 H2SO4 STRONG BASES: LiOH NaOH Sr(OH)2 Ba(OH)2 NOTE ON HIDDEN REACTIONS! LOOK FOR: 1. IF ONE COMPOUND IS AQUEOUS, THAT MEANS THAT IT IS IN WATER, AND THE OTHER COMPOUND MIGHT REACT WITH THAT WATER! 2. IF ONE COMPOUND IS AN ACID OR A BASE, THEN THE OTHER COMPOUND MIGHT REACT WITH WATER TO FORM AN ACID OR A BASE 3. NON-METAL OXIDES THAT REACT WITH WATER 4. METAL OXIDES THAT REACT WITH WATER V) Organic Reactions a. Addition Reactions b. Substitution Reaction c. Combustion Reactions (oxidation of an organic molecule) - Usually have the general form: Organic Molecule + O2 -------------> CO2 + H2O - Can produce CO and C with incomplete combustion (lack of O2) Organic molecule often times is a hydrocarbon – can contain other elements, such as N or S – nitrogen and sulfur oxides are produced d. Esterification e. Saponification VI) Reduction/Oxidation Reactions - - In a reduction/Oxidation reaction, one species is oxidized (loses electrons) and the other species is reduced (gains electrons) The species being oxidized is called the “reducing agent” and the species being reduced is called the “oxidizing agent” Many oxidation/reduction reactions will occur in either acidic or basic solution, taking advantage of H+ or OH- ions, along with H2O, to aid the reduction/oxidation These reactions are written and balanced using the half-reaction method There are obvious signs to look for in a common redox reaction: Important Oxidizing Agents (These things are reduced!) MnO4- (acid solution) MnO4- (basic solution) MnO2 (acid solution) Cr2O7-2 (acid solution) CrO4-2 (basic solution) HNO3, concentrated HNO3, dilute H2SO4, hot concentrated Metallic Ions Free Halogens HClO4 Na2O2 H2O2 Perhalates, halates, halites Formed in Reaction Mn+2 MnO2 Mn+2 Cr+3 Cr+3 NO2 NO SO2 Metallous Ions Halide Ions Cl-1 OH-1 H2O Halogens Important Reducing Agents (These things are oxidized!) Halide Ions Free Metals Metallous Ions Sulfite Ions, SO2 Free Halogens (dilute basic solution) Free Halogens (concentrated basic solution) C2O4-2 NO2-1 Sn+2 H2O2 Formed in Reaction Halogens Metal Ions Metallic Ions SO4-2 Hypohalite Ions Halate Ions CO2 NO3-1 Sn+4 O2 Chromium: dichromate to Cr3+ in acid solution; chromate to Cr(OH)3 in basic solution. Dichromate ion can turn into chromate in basic solution, and chromate ion can turn into dichromate ion in acidic solution (this is not reduction/oxidation – the Cr still retains a +6 charge) Oxygen: hydrogen peroxide can acts as an oxidizing agent (reduced to water) and a reducing agent (oxidized to oxygen gas). Nitrogen: nitrate ion is an oxidizing agent only in acid solution. The reduction product is NO. Sulfur: sulfate ion is an oxidizing agent only in acid solution. The reduction product is SO2. VII) Complex Ion Reactions (Coordination Chemistry) a. b. c. d. e. f. Transition metal salt + ligand → complex ion Aluminum salt + ligand → complex ion Beryllium salt + ligand → complex ion Both Zn+2 and Al+3 form Zn(OH)4-2 and Al(OH)4-1 when treated with excess hydroxide Ag+1, Cu+2, Zn+2, and Cd+2 all form complexes with NH3 Infrequently seen, but has been on the AP, and used in lab: 1. Thiocyanate acts as a ligand and bonds to a transition metal a. A drop of potassium thiocyanate is added to a solution of iron (III) chloride: SCN-1 + Fe+3 → Fe(SCN)+2 2. Ammonia, as a ligand, gets turned into ammonium ion, and the transition metal is freed from being a complex ion a. Dilute hydrochloric acid is added to a solution of diamminesilver (I) nitrate: H+1 + Cl-1 + [Ag(NH3)2]+2 → AgCl + NH4+1 Notice the destruction, rather than the formation, of a complex Common ligands are: Cl-, I-1, Br-1, F-1, OH-1, H2O, C2O4-2, NH3, SCN-1, CN-1 It is a good idea to recognize the names of these ligands as well – iodo, bromo, fluoro, hydroxy, aqua, oxalato, ammine, thiocyanato or isothiocyanato, and cyano To determine the coordination number: - For aqua complexes of transition metals, C.N. = 6 For others, C.N. = cation charge x 2 VIII) Lewis Acid and Lewis Base Reactions a. Lewis acid reacts with a Lewis base to form an adduct: - BF3 + NH3 → F3BNH3 b. Phosphorus (V) oxytrichloride is added to water - POCl3 + H2O → H3PO4 + Cl- + H+ c. Note that molecular phosphorus compounds form acids with water. - PCl5 + H2O → H3PO4 + H2O + Cl- + H+ - PCl3 + H2O → H3PO3 + Cl- + H+ d. Organic bases that have unshared pairs of electrons can react with water or other H+ suppliers: - Methylamine gas is bubbled into water: - CH3NH2 + H2O → CH3NH3+ + OH¯