Oxidation Numbers, Reactions in Aqueous Solutions, & Predicting Products

I. Rules for Assigning Oxidation Numbers 1. The oxidation number of any uncombined element is The oxidation number of a monatomic ion equals the charge on the ion. 3. The more-electronegative element in a binary compound is assigned the number equal to the charge it would have if it were an ion. 4. The oxidation number of fluorine in a compound is always Oxygen has an oxidation number of -2 unless it is combined with F (when it is +2), or it is in a peroxide (such as H 2 O 2 or Na 2 O 2 ), when it is The oxidation state of hydrogen in most of its compounds is +1 unless it is combined with a metal, in which case it is -1.

Oxidation vs. Reduction The sum of the oxidation states in a neutral compound must equal zero and must be equal to the overall charge in an ionic compound. The sum of the oxidation states in a neutral compound must equal zero and must be equal to the overall charge in an ionic compound. Assign oxidation states to each of the atoms in the following compounds: a. FeF 2 b. H 2 O c. KMnO 4 d. C 2 H 6 e. I Cl 5 f. SO (-1)1(+2)1(-2)2(+1)4(-2)1(+1)+7 6(+1)2(-3)5(-1)+54(-2)+6 Fe = + 2, F = - 1 C = - 3, H = + 1 H = + 1, O = - 2 K = + 1, Mn = + 7, O = - 2 I = + 5, Cl = - 1 S = + 6, O = - 2 Assign oxidation states to each atom in the equation. Fe 2 O Al  Al 2 O Fe Fe gains electrons. It has been REDUCED Al lost electrons. It has been OXIDIZED = -2

Remember LEO GER:LOSE ELECTRONS OXIDATION GAIN ELECTRONS REDUCTION Something that is reduced is called an oxidizing agent. Something that is oxidized is called a reducing agent. For each reaction, identify that atoms that undergo reduction, or oxidation. a. 2 H 2 (g) + O 2 (g)  2 H 2 O (g) b. Zn (s) + Cu 2+ (aq)  Zn 2+ (aq) + Cu (s) c. 2 AgCl (s) + H 2 (g)  2 H + (aq) + 2 Ag (s) + 2 Cl - (aq) d. 2 MnO 4 - (aq) + 16 H + (aq) + 5 C 2 O 4 2- (aq)  2 Mn 2+ (aq) + 10 CO 2(g) + 8 H 2 O (l) oxidized: hydrogen (0 to +1) reduced: oxygen (0 to -2) oxidized: zinc (0 to +2) reduced: copper (+2 to 0) oxidized: hydrogen (0 to +1) reduced: silver (+1 to 0) oxidized: carbon (+3 to +4) reduced: manganese (+7 to +2) II. REDOX Reactions

Learning Check Assign oxidation states to each of the atoms in the following compounds: a. SO 2 b. S c. SO 3 Assign oxidation states to each atom in the equation. Determine which element was oxidized and which was reduced. 2 Al + 3 CuCl 2  2 AlCl Cu

When a soluble ionic salt dissolves in water the ions separate and a hydration shell is formed around each ion (Dissociation) Ex. Ba(NO 3 ) 2 in water – Ba(NO 3 ) 2 (aq)  Ba +2 (aq) + 2 NO 3 -1 (aq) Al(C 2 H 3 O 2 ) 3 (aq)  Al +3 (aq) + 3 C 2 H 3 O 2 -1 (aq) Al 2 (CO 3 ) 3 (s)  Al 2 (CO 3 ) 3 (s) or No RXN Aluminum acetate Aluminum carbonate III. Dissociation

Draw a beaker of dissociated sodium chloride; a beaker of dissociated Aluminum nitrate; and a beaker of silver chloride. Na +1 Cl -1 Na +1 Cl -1 Na +1 = sodium ion = chloride ion Al +3 NO 3 -1 Al +3 NO 3 -1 = aluminum ion = nitrate ion Cl -1 Ag +1 Cl -1 Ag +1 Cl -1 Ag +1 = silver ion = chloride ion

Learning check Write a dissociation equation for aluminum sulfate Write a dissociation equation for aluminum sulfate Draw a beaker of dissociated aluminum sulfate Draw a beaker of dissociated aluminum sulfate

IV. Predicting Products A. Single Displacement reactions: an element and a compound combine to form a new element and compound. * Use the activity series. General Equation: Example: A + YB  Y + AB (Cation)B + AZ  Z + AB (Anion) Sodium + Lead (II) acetate Na +1 Pb +2 C 2 H 3 O 2 -1 Na (s) + Pb(C 2 H 3 O 2 ) 2(aq)  Pb (s) + NaC 2 H 3 O 2 (aq) 22 *If you don’t know the charge use +2

Single Replacement Reactions: Activity Series Active metal elements can replace less active metals, active nonmetal elements can replace less active nonmetals. Active metal elements can replace less active metals, active nonmetal elements can replace less active nonmetals. Use the Activity series (snoopy sheet) to determine whether or not the reaction will occur. Use the Activity series (snoopy sheet) to determine whether or not the reaction will occur. Driving force is the transfer of electrons. Driving force is the transfer of electrons.

Learning check Try these single displacement reactions: Try these single displacement reactions: 3. copper + silver nitrate 4. bromine + sodium chloride

Lab – Metal Activity and Reactivity

B. Double Displacement reactions: two compounds combine to produce two different compounds - Acid-Base and Precipitation Reactions. * Use solubility rules. General Equation: Example: AB + YZ  AZ + YB Lead (II) acetate + sodium chloride Pb(C 2 H 3 O 2 ) 2 (aq) + NaCl  PbCl 2 (s) + NaC 2 H 3 O 2 (aq) 22 Driving force = liquid Driving force = solid Pb +2 C 2 H 3 O 2 -1 Na +1 Cl -1

Learning check Try these double displacement reactions: sodium sulfate + lead (II) nitrate sodium sulfate + lead (II) nitrate sulfuric acid + potassium hydroxide sulfuric acid + potassium hydroxide

Molecular Equation: shows the complete formula of all reactants and products Ex: Complete Ionic Equation: represents aqueous compounds as ions Ex: Net Ionic Equation: includes only those components directly involved in the reaction. Ions present on both sides on the equation and do not participate directly in the reaction are called Spectator Ions Ex: Silver nitrate + barium chloride Ag +1 NO 3 -1 Ba +2 Cl -1 AgCl AgNO 3 (aq) + BaCl 2 (aq)  (s) + Ba(NO 3 ) 2 (aq) 2 2 Ag +1 (aq) NO 3 -1 (aq) Ba +2 (aq) 2Cl -1 (aq)  2AgCl (s) Ba +2 (aq) 2NO 3 -1 (aq) 2Ag +1 (aq) + 2Cl -1 (aq)  2AgCl (s) Complete Ionic and Net Ionic Equations

Ex: Write the molecular, complete ionic and net ionic equations for the following reaction. Sodium + Zinc Nitrate Zn +2 NO 3 -1 Na +1 Molecular – 2 Na (s) + Zn(NO 3 ) 2(aq)  Zn (s) + 2NaNO 3(aq) 2 Na (s) + Zn +2 (aq) + 2 NO 3 -1 (aq)  Zn (s) + 2 Na +1 (aq) + 2 NO 3 -1 (aq) Net – 2 Na (s) + Zn +2 (aq)  Zn (s) + 2 Na +1 (aq) Complete -

C. Decomposition reactions: a single compound is broken down into more than one product. There are six different types. 1. Decomposition of a binary compound into its elements. * Usually requires heat or electricity. General Equation: Example: 2. Decomposition of a base into a metal-oxide and water. General Equation: Example: AB  A + B Δ = heat or electricity Sodium Chloride NaCl (aq) + Na (s)  Cl 2(g) 22 AOH  AO + H 2 O Sodium Hydroxide NaOH (aq) +  H 2 O (l) 2 Base = Compound that contains hydroxide (OH -1 ) A is metal/cation, B is nonmetal/anion Na 2 O (s) Metal-oxide = solid

3. Decomposition of a ternary acid into a nonmetal-oxide and water. General Equation: Example: 4. Decomposition of a metallic carbonate into a metal-oxide and carbon dioxide. General Equation: Example: HBO  BO + H 2 O sulfuric acid H 2 SO 4(aq) +  H 2 O (l) ACO 3  AO + CO 2 Sodium Carbonate Na 2 CO 3(aq) +  CO 2(g) SO 3(g) nonmetal-oxide = gas Na 2 O (s) A is metal/cation, B is nonmetal/anion

5. Decomposition of a metallic chlorate into a metal-chloride and oxygen gas. 5. Decomposition of a metallic chlorate into a metal-chloride and oxygen gas. General Equation: Example: 6. Decomposition of a tertiary salt into a metal- oxide and a non-metal oxide General Equation: Example: AClO 3  ACl + O 2 Sodium Chlorate NaClO 3(aq) +  O 2(g) 22 ABO  AO+ BO Sodium Phosphate Na 3 PO 4(aq) +  P 2 O 5(g) 23 NaCl (aq) 3 Na 2 O (s) A is metal/cation, B is nonmetal/anion

Special Situations Whenever H 2 CO 3, H 2 SO 3, or NH 4 OH is a product it will decompose immediately as follows: Whenever H 2 CO 3, H 2 SO 3, or NH 4 OH is a product it will decompose immediately as follows: H 2 CO 3  H 2 O + CO 2 H 2 CO 3  H 2 O + CO 2 H 2 SO 3  H 2 O + SO 2 H 2 SO 3  H 2 O + SO 2 NH 4 OH  H 2 O + NH 3 NH 4 OH  H 2 O + NH 3

Learning check Try these decomposition reactions: Try these decomposition reactions: 5. Calcium chlorate 6. Phosphoric acid 7. Barium hydroxide 8. Tin (IV) carbonate

Synthesis reactions: two substances combine to form one product. There are four different types. 1. Two elements combine to form a binary compound. General Equation: Example: 2. Combining a metal-oxide and water to produce a base. General Equation: Example: A is metal/cation, B is nonmetal/anion A + B  AB Sodium + Chlorine NaCl (aq) + Na (s)  Cl 2(g) 22 AO + H 2 O  AOH Barium oxide + water Ba(OH) 2(aq) + BaO (s)  H 2 O (l)

3. Combining a nonmetal–oxide and water to produce a tertiary acid. General Equation: Example: 4. Combining a metal-oxide and a nonmetal- oxide to produce a tertiary salt. General Equation: Example: BO + H 2 O  HBO dinitrogen pentoxide + water HNO 3(aq) + N 2 O 5(g)  H 2 O (l) 2 AO + BO  ABO Barium oxide + dinitrogen pentoxide Ba(NO 3 ) 2(aq) + BaO (s)  N 2 O 5(g) A is metal/cation, B is nonmetal/anion

Learning check Try these synthesis reactions: Try these synthesis reactions: 9. Water + magnesium oxide 10. Water + dinitrogen trioxide 11. Bromine + sodium

Combustion reactions: Certain organic compounds (Hydrocarbons – compound containing Carbon and Hydrogen or Carbon, Hydrogen and Oxygen) burn to produce specific products. There are two types. 1. Complete combustion – combining a hydrocarbon with excess oxygen to produce carbon dioxide and water. * if the equation does not indicate limited oxygen assume complete combustion General Equation: Example: 2. Incomplete combustion - combining a hydrocarbon with limited oxygen to produce carbon monoxide and water. General Equation: Example: C x H x + O 2  CO 2 + H 2 O C x H x + limited O 2  CO + H 2 O CH 4(g) + limited O 2(g)  CO (g) + CH 4(g) + O 2(g)  CO 2(g) +H 2 O (g) H 2 O (g)

Learning check Try these combustion reactions: Try these combustion reactions: 12. C 8 H 18 + oxygen 13. C 2 H 2 + oxygen

Reaction rate depends on the collisions between reacting particles. Reaction rate depends on the collisions between reacting particles. Successful collisions occur if the particles... Successful collisions occur if the particles... with each other with each other have the correct have the correct have enough to break bonds have enough to break bonds collide orientation kinetic energy V. Reaction Rates

To speed up the rate of the reaction: To speed up the rate of the reaction: Increase (smaller particles or dissolve in water) Increase (smaller particles or dissolve in water) Increase (add more reactant) Increase (add more reactant) Increase (add heat source) Increase (add heat source) Add Add surface area concentration temperature catalyze/enzyme

Exothermic reactions release heat Exothermic reactions release heat Heat is a product Heat is a product Feels hot Feels hot Endothermic reactions absorb heat Endothermic reactions absorb heat Heat is a reactant Heat is a reactant Feels cold Feels cold VI. Heat in Reactions