Chemical Equations

Review: Chemical Reactions Chemical Reaction Chemical Reaction Bonds from reactants are broken, atoms are rearranged to form new substances (products) Bonds from reactants are broken, atoms are rearranged to form new substances (products) Chemical reactions are represented by chemical equations Chemical reactions are represented by chemical equations Evidence of Chemical Reaction Evidence of Chemical Reaction Color Change Color Change Gas Evolution Gas Evolution Change in temperature without heating/cooling Change in temperature without heating/cooling Precipitate Formation Precipitate Formation New Substance forms New Substance forms

Review: Chemical Reactions Reactants Reactants what you start with what you start with what “reacts” together and are used up as products form what “reacts” together and are used up as products form Left side of arrow Left side of arrow Products Products what you produce at the end what you produce at the end formed during the chemical reaction formed during the chemical reaction Right side of arrow Right side of arrow Reactants and products can be solids (s), liquids (l), gases (g), or dissolved in water, aqueous (aq) Reactants and products can be solids (s), liquids (l), gases (g), or dissolved in water, aqueous (aq)

Symbols  “yields” and separates reactants from products “yields” and separates reactants from products + Separates reactants from each other or products from each other Separates reactants from each other or products from each other (s) (s) solid solid (l) (l) liquid liquid (g) (g) gas gas

Symbols ∆ Heat is added Heat is added xy xy Catalyst is present Catalyst is present

Fe (s) + Cl 2(g)  FeCl 3 (s) Reactants: Fe, Cl 2 Products: FeCl 3 Which are solids: Fe, FeCl 3 Which are gases: Cl 2 Solid iron reacts with chlorine gas to yield solid iron chloride

Classifying Chemical Rxns Synthesis Synthesis Reaction where 2 or more substances react to produce ONLY 1 product Reaction where 2 or more substances react to produce ONLY 1 product A + B  AB 2Fe + 3Cl 2  FeCl 3 2Fe + 3Cl 2  FeCl 3 N 2 + 3H 2  2NH 3 N 2 + 3H 2  2NH 3

Classifying Chemical Rxns Combustion Combustion Reaction where oxygen gas is a reactant, and heat/light are released Reaction where oxygen gas is a reactant, and heat/light are released 2SO 2 + O 2  2SO 3 2SO 2 + O 2  2SO 3 4Al + 3O 2  2Al 2 O 3 4Al + 3O 2  2Al 2 O 3

Classifying Chemical Rxns Decomposition Decomposition Reaction where ONLY 1 reactant breaks down into 2 or more products. Reverse of synthesis Reaction where ONLY 1 reactant breaks down into 2 or more products. Reverse of synthesis AB  A + B 2H 2 O  2H 2 + O 2 2H 2 O  2H 2 + O 2 2KClO 3  2KCl + 3O 2 2KClO 3  2KCl + 3O 2

Classifying Chemical Reactions Single Replacement Single Replacement Atoms of 1 element replace atoms of another element in a compound Atoms of 1 element replace atoms of another element in a compound Leaves a different element “alone” on the product side Leaves a different element “alone” on the product side A + BC  AC + B Fe + CuCl 2  FeCl 2 + Cu Fe + CuCl 2  FeCl 2 + Cu Mg + 2HCl  MgCl 2 + H 2 Mg + 2HCl  MgCl 2 + H 2

Classifying Chemical Reactions Double Replacement Double Replacement Cations and anions in 2 compounds replace each other Cations and anions in 2 compounds replace each other AB + CD  AD + BC 2NaOH + H 2 SO 4  Na 2 SO 4 + 2HOH 2NaOH + H 2 SO 4  Na 2 SO 4 + 2HOH NaCl + AgNO 3  NaNO 3 + AgCl NaCl + AgNO 3  NaNO 3 + AgCl

METALS Lithium Lithium Rubidium Rubidium Potassium Potassium Calcium Calcium Sodium Sodium Magnesium Magnesium Aluminum Aluminum Manganese Manganese Zinc Zinc Iron Iron Nickel Nickel Tin Tin Lead Lead Copper Copper Silver Silver Platinum Platinum Gold GoldHALOGENS Fluorine Fluorine Chlorine Chlorine Bromine Bromine Iodine Iodine

Model for Rxn Rates – Vocab Reaction Rate Reaction Rate Δ in [reactant] or [product] per unit time Δ in [reactant] or [product] per unit time How fast the reactants turn into products How fast the reactants turn into products Collision Theory Collision Theory Atoms, ions, and molecules must collide in order to react Atoms, ions, and molecules must collide in order to react They need to collide with a certain amount of E and in a certain orientation in order for the rxn to occur They need to collide with a certain amount of E and in a certain orientation in order for the rxn to occur

Model for Rxn Rates – Vocab Activated Complex Activated Complex Temporary, unstable arrangement of atoms that may either form products, or reform reactants Temporary, unstable arrangement of atoms that may either form products, or reform reactants Called the transition state Called the transition state Activation Energy Activation Energy Minimum amount of E needed for reactants to form the activated complex Minimum amount of E needed for reactants to form the activated complex Minimum amount of E for a chemical rxn to occur Minimum amount of E for a chemical rxn to occur

Model for Rxn Rates – Vocab Exothermic Reaction Exothermic Reaction E is released as heat E is released as heat Reactants have more E than products Reactants have more E than products “ThermaCare” or a hot pack “ThermaCare” or a hot pack Endothermic Reaction Endothermic Reaction Energy is taken in Energy is taken in Reactants have less E than products Reactants have less E than products “Cold Packs” “Cold Packs”

Exothermic Reactions

Endothermic Reactions

Factors Affecting Rxn Rates Concentration Concentration Measure of solute in a solution Measure of solute in a solution [Increase]  more collisions  faster rate [Increase]  more collisions  faster rate Surface Area Surface Area Amount of substance exposed Amount of substance exposed Smaller size  inc. SA  more collisions  faster rate Smaller size  inc. SA  more collisions  faster rate

Factors Affecting Rxn Rates Temperature Temperature Measure of avg. kinetic E of particles Measure of avg. kinetic E of particles Inc. temp  inc KE and speed of particles  more collisions  faster rate Inc. temp  inc KE and speed of particles  more collisions  faster rate Catalyst Catalyst Substance increases rate of chem rxn by lowering Eact. Substance increases rate of chem rxn by lowering Eact. Catalysts are not consumed in the rxn Catalysts are not consumed in the rxn Heterogenous – different physical state than the rxn Heterogenous – different physical state than the rxn Homogenous – same physical state as rxn Homogenous – same physical state as rxn Catalyst  lower Eact  more collisions  faster rate Catalyst  lower Eact  more collisions  faster rate

Factors Affecting Rxn Rates Inhibitor Inhibitor Substance that slows down rxn rates Substance that slows down rxn rates Can sometimes prevent rxn from occurring Can sometimes prevent rxn from occurring Inhibitor  decrease rxn rate Inhibitor  decrease rxn rate Examples: Examples: Food preservatives inhibit spoiling by bacteria Food preservatives inhibit spoiling by bacteria Anti-histamines inhibit allergy symptoms from allergen Anti-histamines inhibit allergy symptoms from allergen Ibuprofen inhibits inflammation of areas by stopping the buildup of red blood cells Ibuprofen inhibits inflammation of areas by stopping the buildup of red blood cells