Kinetics/Equilibrium; Acids/Bases & Organic Chemistry Welcome To The GowerHour Unit 12 (Chapter 18): Chemical Kinetics I. Chemical kinetics: The study of reaction ______( ________ of rates Speed reaction). A. Factors that influence the reaction ______. rate 1. _______________ of reactants. Concentration 2. Nature of the reaction (Amount of _________________). Activation energy 3. _________________ Temperature 4. Reaction mechanism 5. Presence of a __________. catalyst B. Collision Theory collisions reactants 1. Reactions occur when there are ________ between __________. 2. BUT...not all __________ lead to a reaction. collisions oriented geometry a. Molecules must be properly ________ (collision___________). Example: CO + NO2 → CO2 + NO O O C Ineffective C Effective N O collision O collision ON O kinetic energy KE b. Only molecules with enough _____________(_____) to break the bonds reaction _______ will result in a __________. (KE > Ea) KE bounce c. Molecules with low _____ (KE < Ea) will _________ off of each No reaction other (____________). C. Activation Energy (EA) 1. Always a _________quantity. positive 2. Depends on the ________ of the reaction. nature Low a. Fast reaction = _____EA High b. Slow reaction = ______EA 3. Independent of ______________ and _____________. concentration temperature 4. Catalyst _________ EA without being __________ in the lowers consumed reaction. 5. Diagram of activation energy w/ catalyst (Lowers EA) products E Activation energy (EA) react E = energy rxn progress E = energy * * = Activated complex react Activation energy (EA) E w/ catalyst (Lowers EA) products rxn progress intermediate 6. Activated complex = ____________ between reactants and products (________________) Pseudo-molecule 7. Example of activated complex: CO + NO2 → CO2 + NO Reactants O C + O N O Activated complex O C O N O = partial bond Very Unstable Products O C O+ N O D. Reaction Rate and Temperature As temperature __, rate __ (in general) T2 > T1 Average KE increases w/ # of temperature molecules More molecules have KE > EA at higher T T2 T1 EA KE **Activation Energy is a fixed amount, independent of temperature E. Collision Theory--Qualitative effects: 1. particle size size ; surface area ; collisions ; rate As the size of the particle , the rate 2. temperature T ; KE ; the # of molec. w/ min energy ; rate As the temperature , the rate 3. catalysts As the EA , the rate 4. concentration concentration ; the # of molec.; the # of collisions ; rate As the concentration , the rate F. Reaction rate: A positive quantity that expresses how the Molarity concentration (_________) of a reactant or product changes with ______. time [X] = concentration of X (M) X mol/L·s Units of Rate: _____________ Rate time 1. Example: 2 N2O5 → 4 NO2 + O2 Reactants decrease () over time, products increase (+) over time. N 2O5 NO2 O 2 rate = 2 t 4 t 1 t coefficients 2. 2 N2O5 4 NO2 + O2 [NO2] 4 Conc 2 (M) 1 [O2] 0 [N2O5] Time H. Reaction Mechanism: Sequence of steps by which a reaction occurs on the __________ level (like Hess’ Law) molecular 1. Example: CO + NO2 CO2 + NO 1. NO2 + NO2 NO3 + NO Elementary step 2. CO + NO3 CO2 + NO2 Elementary step Overall: CO + NO2 CO2 + NO 2. Rate determining step: slowest The _________ step in the reaction mechanism. a. Example: AB fast BC fast CD slow Rate determining step! Overall rxn: A D Overall rate ______ Rate of the slowest step. E A B C D Rxn II. Equilibrium A. Reversible Reactions: Reactions that do not go to ___________. completion Example: 1. H + I → 2 HI 2 2 pink clear 2. Phenolphthalein (ph) ph+ + H+ → ph-H+ exothermic Example: Rechargeable battery Pb + PbO2 + 2 H2SO4 → 2 PbSO4 + 2 H2O + energy Add electricity & the rxn will reverse B. Equilibrium system: The ________ and _______ reactions occur forward reverse _____________ at the same ____(______) and the concentrations of reactants and rate speed products remain _________. constant Rateforward = Ratereverse C. Equilibrium is a dynamic process: At equilibrium the _________ and _______ reactions are still occurring forward reverse dynamic constant (_________), even though the concentrations remain _________. Example: changing classrooms Concentration of reactants + products do not need to be equal ….. only the rates! equilibrium D. Stresses alter equilibrium: When a system is at ____________, changes it will stay that way until something ________ this condition. Stresses: (1) temperature (2) concentration (3) pressure E. Le Chatelier’s Principle: When a system at equilibrium is disturbed by applying a ______, a new ____________ position is stress equilibrium relieve attained to _______ the stress. 1. Temperature effects on equilibrium Example: 2 NO2 → N2O4 + 58.8 kJ (exothermic) heat (a) STRESS: Raise temperature (addition of ______) Equilibrium is shifted ____. left (b) STRESS: Lower temperature (removal of ______) heat right Equilibrium is shifted ______. 2. Pressure effects on equilibrium: When pressure is __________, the stress is relieved by favoring the reaction increased with _______ gas molecules (fewer gas molecules = ______ fewer lower pressure). Example: 2 NO2 (g) → N2O4 (g) (a) STRESS: Increase pressure 2 molecules on left, 1 molecule on the right (lower pressure) Equilibrium is shifted _______. right (fewer gas molecules) (b) STRESS: Decrease pressure Equilibrium is shifted ______. (greater # of gas molecules) left 3. Concentration effects on equilibrium: Example: Acid/Base indicator [Ni(H2O)6]2+ + 6 NH3 → [Ni(NH3)6]2+ + 6 H2O green blue (a) STRESS: Add NH3 Need to remove NH3 Right (blue) Equilibrium is shifted _____________. (b) STRESS: Add H2O Need to remove H2O Equilibrium is shifted _____________. Left (green) F. Applications of Le Chatelier’s Principle 1. Glasses / Sunglasses Reaction: AgCl + energy → Ag + Cl clear dark STRESS: Add sunlight energy, shifts right, glasses become dark. STRESS: Remove sunlight energy, shifts left, glasses become clear. 2. Biochemical Equilibrium System (Respiration) Reactions: CO2 + H2O → H2CO3 CO2 formed H2O during respiration H2CO3 → H+ + HCO3- More CO2 produced STRESS: Exercise vigorously __________________) Both rxns shift right. [H+] (Acid) causing pH (acidic) the brain sends a message to exhale more rapidly. exhale CO2 STRESS: Breathe faster (___________) Less CO2, Rxns shift left, [H+] , & pH returns to normal. 3. Hyperventilating (See above reactions) exhale a lot of CO2 STRESS: Exhale rapidly (_________________) Rxn shifts left, pH (alkaline), body responds by constricting blood vessels (dizziness). Breathe in exhaled CO2 STRESS: Breathe into bag (_______________________) Rxn shifts back to the right. 4. Altitude Sickness Reaction: Hb + O2 → Hb–O2 (Hemoglobin) (Oxygen circulates in blood) STRESS: Lower pressure (________________________) Lower concentration of O2 Rxn shifts left (less O2 to brain/body, which leads to dizziness, nausea, & headache) STRESS: Increase hemoglobin production (Acclimation) Body adjust by producing hemoglobin, shifting the rxn back to the right, more O2 circulates in body. G. How is equilibrium measured? Equilibrium Expression 1. Keq = Equilibrium constant (No Units) Concentration (a) Kc (_____________); Used for solutions (aq) or gases. (b) (b) Kp (________); Used for gases only. Pressure 2. Equilibrium Expression Reaction: aA + bB cC + dD c d [products] [C] [D] K eq K eq a b [reactants] [A] [B] Kc equilibrium (a) Concentrations are at____________. (Not _____ concentration) initial (b) Concentration = mol / L container Some books call this Molarity! L S negligible (c) Amount of pure __ or __ consumed in a reaction is _________, so Equilibrium expression they are not included in the ____________________. Example: Calculate the molarity of 1.00 L of water. Intensive 1000 g x 1 mol 1.00 L = 1000 g = 55.5 mol property: depends 18.02 g 55.5 mol upon density! Large! M (d) Meaning of equilibrium constant: L forward 1. Keq > 1 : Products are favored. (________ reaction) ________ 2. Keq < 1 : _________ are favored. (_______ reaction) Reactants reverse (e) What does a Keq of 1.0 x 1030 mean? 1.0 x 10-30? Products >> Reactants Reactants >> Products (Almost complete) 3. Example: (a) Write the equilibrium expressions, Kc, for the following reaction: 2 NO2(g) 2 NO(g) + O2(g) 2 [NO] [O2 ] KC 2 [NO2 ] 4. Example: PCl5(g) PCl3(g) + Cl2(g) For the above reaction, the equilibrium constant is 35. If the concentrations of PCl5 and PCl3 are 0.015 M and 0.78 M respectively. What is the concentration of Cl2? [PCl 3 ][Cl 2 ] K eq [PCl 5 ] (0.78)[Cl2 ] 35 [Cl2] = 0.67 M 0.015 H. Calculating equilibrium concentrations from initial concentrations: Steps in calculating equilibrium concentrations: (1) Write equilibrium expression (2) Calculate change in concentration of each substance (3) Calculate equilibrium concentrations Example #1: Given the following reaction: A B + C. The initial concentration of A is 0.260 M and at equilibrium, [C] is 0.160 M. Calculate the Kc. Kc = ? A B + C Initial (M) 0.260 0 0 Change (M) x + x + x 0.160 + 0.160 + 0.160 Equilibrium (M) 0.100 0.160 0.160 2 [B][C] (0.160) Kc = 0.256 [A] 0.100 Example #2: Given the following reaction: H2(g) + I2(g) ↔ 2 HI(g). At 25°C, 0.100 mol of H2 and 0.100 mol of I2 react in a 1.00 L container. At equilibrium, the [H2] is 0.080 M. Calculate Kc at this temperature. M = mol / L H2 + I2 2 HI Initial (M) 0.100 0.100 0 Change (M) x x + 2x 0.020 0.020 + 0.040 Equilibrium (M) 0.080 0.080 0.040 2 [HI] (0.040) 2 Kc = 0.25 [H2 ][I2 ] (0.080) 2 I. Polymers I. Polymers: A polymer is a compound with a repeating unit, called a ___________, and contains a ______ molar mass. monomers high A. Types of Polymers 1. Natural polymers: polyisoprene (a) Rubber (______________) (b) Biological compounds: (i) Proteins (ii) Nucleic acids (DNA & RNA) (iii) Cellulose (iv) Starch 2. Synthetic polymers: (a) Nylon (b) Polyester (c) PVC (d) Plexiglass B. Reaction Types 1. Addition reaction: One molecule _____ to another molecule. adds Monomer: _________ ethylene H H C C H H Example: Polyethylene C C C C C C C C C C C C C C C C Addition Reaction Vinyl chloride Monomer: _____________ H H C C H Cl Example: PVC Polyvinyl chloride (____) C C C C C C C C Cl Cl Cl Cl C C C C C C C C Cl Cl Cl Cl The simple repeating unit of a polymer is the monomer. Homopolymer is a polymer made up of only one type of monomer ( CF2 CF2 )n ( CH2 CH2 )n ( CH2 CH )n Teflon Polyethylene Cl PVC 2. H2O Condensation reactions: A ____ molecule is formed in the reaction. · H Amine group (amino): NH2 or N H · O Carboxylic acid group (carboxyl): COOH or C · O H · · Example: Polyester · O O H · C O C · OH + H O CH2 CH2 OH · · · · · · H2O Dehydration synthesis vs Hydrolysis O O H · C O C · O CH2 CH2 OH · · · · · ester · ester Example: Proteins (Alanine + Glycine) Alanine Glycine H O H O H2N C C OH + H2N C C OH CH3 H R group H2O (Dehydration Synthesis) Peptide bond H O H O H2N C C N C C OH + H2O CH3 H H Amino acids are the basic structural units of proteins. An amino acid is a compound that contains at least one amino group (-NH2) and at least one carboxyl group (-COOH) Peptide bond = _______ group : ______________ amide carboxyl group 2 dipeptide = ___ amino acids tripeptide = ___ amino acids 3 many protein polypeptide = ______ amino acids = _______ Example: Glycogen, cellulose, and starch (Polysaccharides) Monomer: _________ glucose Complex carbohydrates CH2OH C O C C or OH HO C C OH OH Glycogen: Animals store energy in the form of glycogen & turn it back into glucose as needed. Cellulose: The most common organic compound on Earth (ie. cotton) Hydrogen Bonds (Cross-linking) Plants use cellulose for strength. The cellulose chains are all stretched out, and like to stay right next to each other, like raw spaghetti that's all stuck together. That's why cellulose can hold up the tallest trees! Starch: Starch is a compact way to store a lot of glucose in a small space. Our bodies break the starch down into glucose, which can be used for energy. Even though starch and cellulose are both made from the same sugar (glucose), they act very differently (because the glucose molecules are joined together differently). Starch will dissolve in water, but cellulose won't. So we make food from starches and we build things and make clothing out of cellulose. Acids & Bases A. Properties of acids and bases: 1. Acids 2. Bases (a) Sour (a) Bitter (b) Changes the color of acid- (b) Changes the color of acid- base indicator. base indicator. (c) Some react w/metals (c) Slippery (d) React w/bases to form salts (d) React w/acids to form salts (e) Conducts electric current (e) Conducts electric current Blue Litmus Paper: Blue to Red Acid Red Litmus Paper: Red to Blue Base B. Bronsted-Lowry Acids and Bases 1. Acids: H+ ________ Donor Example: List of strong acids: HCl (aq) H+ + Cl HNO3, H2SO4, HCl, HCN (aq) H+ + CN HClO4, HBr, HI 2. Bases: H+ ________ Acceptor List of strong bases: LiOH, NaOH, KOH, Example: Ca(OH)2, Ba(OH)2, OH + H+ H2O Sr(OH)2 CN + H+ HCN 3. acid base Amphoteric substances: Can behave like an _____ and a _____. Example: H+ H+ H2CO3 HCO3 H+ + CO32 Contains both a H+ and charge. C. Acid-Base Reactions (Conjugate acid-base pairs) (CA) (Differ by only a H+) 1. HNO2 + ClO HClO + NO2 (CB) Acid Base (CA) 2. H2SO3 + OH H2O + HSO3 (CB) Acid Base (CA) 3. H2CO3 + BrO2 HBrO2 + HCO3 (CB) Acid Base (CA) 4. H3PO4 + C2O42 H2PO4 + HC2O4 (CB) Acid Base C. pH Scale: NaOH N Lye e H2SO4 u t r a l Acidic Alkaline/Basic 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 High quality H2O Acid Rain D. In impure water (contains an acidic or basic substance): If [H+] > 1.0 x 10-7 M, solution is _______. acidic If [H+] < 1.0 x 10-7 M, solution is _________________. basic or alkaline If [H+] = 1.0 x 10-7 M, solution is _________. neutral 1.0 x 10−7 = pH 7 1.0 x 10−2 = pH 2 pH < 7 = acid pH > 7 = base 1.0 x 10−5 = pH 5 pH = 7 = neutral 1.0 x 10−11 = pH 11 The End !!!!
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