Thinking Like a Chemist About Kinetics I UNIT 7 DAY4

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Giles Hensley
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1 UNIT7-DAY4-LaB1230 Page 1 UNIT7-DAY4-LaB1230 Monday, March 25, :51 AM Thinking Like a Chemist About Kinetics I UNIT 7 DAY4 What are we going to learn today? Reaction Rates and the Rate Law Method of Initial Rates IMPORTANT INFORMATION LM28 & LM29 due Th 9AM

2 UNIT7-DAY4-LaB1230 Page 2 IMPORTANT INFORMATION LM28 & LM29 due Th 9AM Talk to LaB or VDB if you are interested in UGTA Quiz: Clicker Question 1 Hydrogen-3 (tritium, H-3) is sometimes formed in the primary coolant water of a nuclear reactor. Tritium is a beta emitter with a t 1/2 = years. For a given sample containing tritium, after how many years will only about 12% of the sample remain? A)12.3 years B)24.6 years C)36.9 years D)49.2 years E)61.5 years

3 Kinetics Kinetics is about how fast chemical reactions occur. Measuring the rates of reactions (macroscopic) gives us insight into the way reactions are actually happening (microscopic) START ACTIVITY! Average, Instantaneous, Initial, Reaction Rate 2NO2(g) 2NO(g) + O2(g) Check in UNIT7-DAY4-LaB1230 Page 3

4 Kinetics Imagine the following reaction CH 3 Cl + OH - CH 3 OH + Cl - Macroscopic Microscopic - [CH 3 Cl] t Check at end of activity -d[ch 3 Cl] = = RATE = dt Measured in lab k[ch 3 Cl][OH - ] Tells us about how The reaction occurs Similar but different reaction: Imagine the following reaction (CH 3 ) 3 CBr + OH - (CH 3 ) 3 COH + Br - - [(CH 3 ) 3 CBr] Macroscopic t -d[(ch3) 3 CBr] = = RATE = dt Measured in lab Microscopic k[(ch 3 ) 3 Br] x [OH - ] y Tells us about how The reaction occurs CH302 Vanden Bout/LaBrake Spring 2012 Poll: Clicker Question 2 Method of Initial Rates-Empirically Determine Rate Law (CH 3 ) 3 CBr + OH - (CH 3 ) 3 COH + Br - What is the rate law for this reaction? Experiment [(CH) 3 CBr]o [OH-]o initial rate (M s -1 ) 1 0.1M 0.1M 2.5 x M 0.1M 5.0 x M 0.2M 2.5 x10-3 UNIT7-DAY4-LaB1230 Page 4

5 UNIT7-DAY4-LaB1230 Page 5 What is the rate law for this reaction? Experiment [(CH) 3 CBr]o [OH-]o initial rate (M s -1 ) 1 0.1M 0.1M 2.5 x M 0.1M 5.0 x M 0.2M 2.5 x10-3 A. Rate = k[(ch 3 ) 3 CBr][OH - ] B. Rate = k[(ch 3 ) 3 CBr][OH - ] 2 C. Rate = k[(ch 3 ) 3 CBr] 2 [OH - ] D. Rate = k[(ch 3 ) 3 CBr] E. Rate = k[oh - ] Vanden Bout Poll: Clicker Question 3 Method of Initial Rates-Empirically Determine Rate Law A + 2B C The reaction is what order in B? Experiment [A]o [B]o initial rate (M s - 1 ) 1 0.1M 0.1M M 0.1M M 0.2M 2.74 A. 0 B. 1 C. 1.5 D. 2 E. 3 Vanden Bout

6 UNIT7-DAY4-LaB1230 Page 6 Method of Initial Rates CH302 Vanden Bout/LaBrake Spring Vanden 2012 Bout Poll: Clicker Question 4 Method of Initial Rates-Empirically Determine Rate Law A + 2B C The reaction is what order in A? Experiment [A]o [B]o initial rate (M s - 1 ) 1 0.1M 0.1M M 0.1M M 0.2M 2.74 A. 0 B. 1 C. 1.5 D. 2 E. 3 Vanden Bout Method of Initial Rates

7 UNIT7-DAY4-LaB1230 Page 7 Method of Initial Rates CH302 Vanden Bout/LaBrake Spring Vanden 2012 Bout Poll: Clicker Question 5 what is k? A + 2B C Experiment [A]o [B]o initial rate (M s -1 ) 1 0.1M 0.1M M 0.1M M 0.2M 2.74 A. 273 M -1 s -1 B s -1 C s -1 D. 614 M -1 s -1 E M s -1 Vanden Bout

8 Method of Initial Rates CH302 Vanden Bout/LaBrake Spring Vanden 2012 Bout Reaction Order The degree to which the reaction rate is dependent on concentrations of species. Order of Each Species Overall Reaction Order Poll: Clicker Question 6 The empirical rate law for the reaction CO + H 2 O CO 2 + H 2 Is rate = k[co][h 2 O] This reaction is overall a A. Zeroth order reaction B. First order reaction UNIT7-DAY4-LaB1230 Page 8

9 UNIT7-DAY4-LaB1230 Page 9 This reaction is overall a 2 A. Zeroth order reaction B. First order reaction C. Second order reaction D. Third order reaction CH302 Vanden Bout/LaBrake Spring 2012 Poll: Clicker Question 7 The empirical rate law for the reaction CO + H 2 O CO 2 + H 2 Is rate = k[co][h 2 O] This reaction is best described as A.First order in CO and first order in H 2 O B.First order in CO only C.Second order in CO D.Second order in CO and second order in H 2 O CH302 Vanden Bout/LaBrake Spring 2012

10 UNIT7-DAY4-LaB1230 Page 10 Poll: Clicker Question 8 The empirical rate law for the reaction CO + H 2 O CO 2 + H 2 Is rate = k[co][h 2 O] What units will the rate constants have? A.M s -1 B.s -1 C.M -1 s -1 D.s -2 CH302 Vanden Bout/LaBrake Spring 2012 Learning Outcomes Understand the concept of rate of change associated with chemical change, recognizing that the rate of change for a chemical reaction can be determined by experimentally by monitoring the change in concentration of a reactant or product with time. Be able to identify the reaction order for a chemical change. Apply integrated rate equations to solve for the concentration of chemical species during a reaction of different orders

Vanden Bout/LaBrake. Important Information. HW11 Due T DECEMBER 4 th 9AM. End of semester attitude survey closes next Monday

Vanden Bout/LaBrake. Important Information. HW11 Due T DECEMBER 4 th 9AM. End of semester attitude survey closes next Monday UNIT4DAY6-LaB Page 1 UNIT4DAY6-LaB Thursday, November 29, 2012 8:13 AM Vanden Bout/LaBrake CH301 The 2 nd Law of Thermodynamics GIBBS FREE ENERGY UNIT 4 Day 6 Important Information HW11 Due T DECEMBER