Chapter 17  pp Reaction Kinetics
17.1 The Reaction Process <ul><li>Explain the concept of  reaction mechanism . </li></ul><ul><li>Use  collision theory  to...
Reaction Mechanisms <ul><li>The  series of steps  that actually occur in a chemical reaction. </li></ul><ul><li>A balanced...
A Molecular Representation of the Elementary Steps in the Reaction of NO 2  and CO   Overall:  NO 2  + CO    NO + CO 2 St...
<ul><li>2NO 2  + F 2   2NO 2 F  </li></ul><ul><li>Rate = k[NO 2 ][F 2 ] </li></ul><ul><li>The  proposed  mechanism is: </l...
<ul><li>Each of the two reactions is called an  elementary step . </li></ul><ul><li>The rate for each reaction can be writ...
Finding the Reaction Mechanism   <ul><li>Must satisfy  two  requirements : </li></ul><ul><li>1. Sum of the  elementary  st...
<ul><li>N 2  + 3H 2   2NH 3   As the reaction progresses the concentration H 2  goes down </li></ul>Concentration Time [H ...
<ul><li>As N 2  + 3H 2   2NH 3  progresses the concentration N 2  goes down 1/3 as fast </li></ul>Concentration Time [H 2 ...
<ul><li>As N 2  + 3H 2   2NH 3  progresses the concentration NH 3  goes up. </li></ul>Concentration Time [H 2 ] [N 2 ] [NH...
Definition of Rate. 2NO 2     2NO + O 2
Collision Theory <ul><li>In order to react molecules and atoms must  touch  each other. </li></ul><ul><li>They must hit ea...
Tr96 Fig. 17-9 p. 533 Possible Collision Patterns
Several Possible Orientations for a Collision Between Two BrNO Molecules.  (a) & (b) can lead to a collision, (c) cannot.
No Reaction O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br
Activation Energy <ul><li>Two things must happen for a reaction to occur. </li></ul><ul><li>Bonds must  break  within the ...
Activation Energy <ul><li>Once an  exothermic  reaction gets started, the energy from bonds  forming  to make products is ...
Energy Reaction coordinate Reactants Products
Energy Reaction coordinate Reactants Products Activation Energy - Minimum energy to make the reaction happen
Energy Reaction coordinate Reactants Products Activated Complex or Transition State
Energy Reaction coordinate Reactants Products Overall energy change
Tr95A A e  Differences in Exothermic & Endothermic Reactions <ul><li>How much bigger is E a (reverse) than E a (forward)? ...
Tr95A A e  Differences in Exothermic & Endothermic Reactions <ul><li>What are the products of the reverse reaction?  . . ....
Detour for STAR Test review <ul><li>The following slides will review the important things you need to know for the STAR te...
Le Châtelier’s Principle <ul><li>If something is changed in a system at equilibrium, the system will respond to relieve th...
Changes in Pressure <ul><li>As the pressure increases the reaction  will shift in the direction of the least gases. </li><...
Changing Concentration N 2(g)  + 3H 2(g)   2NH 3(g)   <ul><li>If you  add reactants  ( i.e. ,  increase  their concentrati...
Changing Concentration N 2(g)  + 3H 2(g)   2NH 3(g) <ul><li>If you  remove   reactants  (or  decrease  their concentration...
Changing Concentration N 2(g)  + 3H 2(g)   2NH 3(g) <ul><li>If you  add products  ( i.e. ,  increase  their  concentration...
Changing Concentration N 2(g)  + 3H 2(g)   2NH 3(g) <ul><li>If you  remove  products (or  decrease  their concentration). ...
Changing Temperature   N 2(g)  + 3H 2(g)   2NH 3(g)  +  92  kJ <ul><li>Reactions either require or release heat. </li></ul...
Exothermic Review   N 2(g)  + 3H 2(g)   2NH 3(g)  +  92  kJ <ul><li> H < 0 </li></ul><ul><li>Releases heat </li></ul><ul>...
Endothermic Review 2H 2 O (g)  + 484 kJ   2H 2(g)  + O 2(g) <ul><li> H > 0 </li></ul><ul><li>Requires heat </li></ul><ul>...
Gas Phase Equilibrium <ul><li>  catalyst   N 2(g)   +  3 H 2(g) 2 NH 3(g)   +  heat high pressure and temperature </li></u...
Le Chatelier Review   pp <ul><li>6CO 2(g)  + 6H 2 O (l)   C 6 H 12 O 6(s)  + 6O 2(g)   ∆H = 2820 kJ </li></ul><ul><li>Some...
Le Chatelier Review   pp <ul><li>6CO 2(g)  + 6H 2 O (l)   C 6 H 12 O 6(s)  + 6O 2(g)   ∆H = 2820 kJ </li></ul><ul><li>Some...
Le Chatelier Review   pp <ul><li>6CO 2(g)  + 6H 2 O (l)   C 6 H 12 O 6(s)  + 6O 2(g)   ∆H = 2820 kJ </li></ul><ul><li>Some...
Radiation <ul><li>Radiation comes from the nucleus of an atom. </li></ul><ul><li>Unstable nucleus emits a particle or ener...
A. Types of Radiation   pp <ul><li>Alpha particle (  ) </li></ul><ul><ul><li>helium nucleus </li></ul></ul>paper 2+ <ul><...
Radiation Protection   <ul><li>Shielding </li></ul><ul><li>alpha – paper, clothing </li></ul><ul><li>beta – lab coat, glov...
Radiation Protection
B. Nuclear Decay   pp <ul><li>Alpha Emission </li></ul>Atomic & Mass Numbers must balance!! parent nuclide daughter nuclid...
B. Nuclear Decay   pp <ul><li>Beta Emission </li></ul><ul><li>Positron Emission </li></ul>electron positron
B. Nuclear Decay   pp <ul><li>Electron Capture </li></ul><ul><li>Gamma Emission </li></ul><ul><ul><li>Usually follows othe...
 
Gamma radiation   pp <ul><li>No change in atomic or mass number </li></ul><ul><li>11 B   11 B  +  0     </li></ul><ul><li...
 
Learning Check NR1   pp <ul><li>Write the nuclear equation for the beta emitter Cobalt-60. . . </li></ul>
Solution NR1   pp <ul><li>Write the nuclear equation for the </li></ul><ul><li>Beta emitter  Cobalt-60. </li></ul><ul><li>...
Producing Radioactive Isotopes <ul><li>Bombardment of atoms produces radioisotopes </li></ul><ul><li>  = 60  = 60 </li></u...
Learning Check NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>1...
Solution NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>10 B  +...
Addition Polymers   pp <ul><li>Polymers are giant molecules, not small like the ones studied earlier in this chapter </li>...
Addition Polymers
17.2 Reaction Rate <ul><li>Define  chemical kinetics  & explain the 2 conditions necessary for chemical reactions to occur...
Kinetics <ul><li>The study of reaction rates. </li></ul><ul><li>Spontaneous reactions are reactions that will happen -  bu...
Things that Affect Rate #1   Nature of Reactants <ul><li>Different substances have different reactivities. </li></ul><ul><...
Things that Affect Rate #2 Surface Area <ul><li>Particle size determines surface area. </li></ul><ul><li>Molecules can onl...
Things that Affect Rate #3 Temperature <ul><li>Higher temperature - faster particles. </li></ul><ul><li>Greater kinetic en...
Things that Affect Rate #4 Concentration <ul><li>More concentrated means the molecules are closer together. </li></ul><ul>...
Tr98 Fig. 17-13 p. 540 Concentration Affects Rate <ul><li>How many collisions can occur between 6 “A” particles & 4 “B” pa...
Things that Affect Rate #5 Catalysts <ul><li>Substances that speed up a reaction  without being used up   ( e.g.,  enzyme)...
Energy Reaction coordinate Reactants Products
Catalysts <ul><li>Speed up a reaction  without being used up  in the reaction. </li></ul><ul><li>Enzymes are biological ca...
Energy Plots for a Catalyzed and an Uncatalyzed Pathway for a Given Reaction. ∆ E  is the same in both cases!
Tr97A Fig. 17-15 p. 541 Comparing Pathways for Decomposing H 2 O 2  by Various Catalysts <ul><li>Why is H 2 O 2  stored in...
Tr97A Fig. 17-15 p. 541 Comparing Pathways for Decomposing H 2 O 2  by Various Catalysts <ul><li>How many activated comple...
<ul><li>Hydrogen bonds to surface of metal. </li></ul><ul><li>Break H-H bonds </li></ul>Catalysts Pt surface H H H H H H H H
Catalysts Pt surface H H H H C H H C H H
Catalysts <ul><li>The double bond breaks and bonds to the catalyst. </li></ul>Pt surface H H H H C H H C H H
Catalysts <ul><li>The hydrogen atoms bond with the carbon </li></ul>Pt surface H H H H C H H C H H
Catalysts Pt surface H C H H C H H H H H
Heterogenous Catalysts <ul><li>Summary:  usually in 4 steps: </li></ul><ul><li>Adsorption & activation  of reactants onto ...
Homogenous Catalysts <ul><li>Chlorofluorocarbons catalyze the decomposition of ozone. </li></ul><ul><li>Both are in same p...
Catalysts and rate <ul><li>Catalysts will speed up a reaction  but only to a certain point . </li></ul><ul><li>Past a cert...
Catalysts and rate. <ul><li>Rate increases until the active sites of catalyst are filled. </li></ul><ul><li>Then rate is  ...
Rate Laws:  An Introduction <ul><li>Reactions are reversible. </li></ul><ul><li>As products accumulate they can begin to t...
<ul><li>Two key points </li></ul><ul><li>The concentration of the  products  do  not  appear in the rate law because this ...
Rate Laws <ul><li>N 2  + 3H 2     2NH 3 </li></ul><ul><li>When forward & reverse reaction rates are equal then there is no...
<ul><li>You will find that the rate will only depend on the concentration of the  reactants . </li></ul><ul><li>Rate =  k ...
Definition of Rate. 2NO 2     2NO + O 2
Determining Rate Laws <ul><li>The  first  step is to determine the  form  of the rate law (especially its  order ). </li><...
The method of Initial Rates <ul><li>This method requires that a reaction be run several times (do in AP Chem). </li></ul><...
Rate Law Example  pp <ul><li>Write the general form of rate law for: BrO 3 -  + 5 Br -  + 6H +   3Br 2  + 3 H 2 O </li></u...
Example Continued  pp <ul><li>So, for the reaction    BrO 3 -  + 5 Br -  + 6H +   3Br 2  + 3 H 2 O The general form of the...
<ul><li>Now we have to see how the  rate  changes with  concentration </li></ul>Initial concentrations (M)   pp Rate (M/s)...
<ul><li>Find  n  by ratio of Rate 2/Rate 1, in which only [BrO 3 - ] changes </li></ul><ul><li>n  = 1 because (next slide)...
The math  pp <ul><li>Rate 2  = 1 .6 x 10 -3  mol/Ls  =  k(0.20 mol/L) n (0.10 mol/l) m (0.10 mol/L) p   Rate 1  8.0 x 10 -...
<ul><li>Find  m  by ratio of Rate 3/Rate 2, in which only [Br - ] changes </li></ul><ul><li>m  = 1 (ditto on math) </li></...
<ul><li>Find  p  by ratio of Rate 4/Rate 1, in which only [H + ] changes </li></ul><ul><li>p  = 2 (next slide) </li></ul>I...
<ul><li>When double [H 1+ ] the rate quadruples so  p = 2 </li></ul><ul><li>Double : quadruple = 2 : 4 = 2 : 2 2   </li></...
Example continued  pp <ul><li>So, rate of reaction is  first  order in BrO 3 -   and  Br -  and  second  order in H + </li...
Rate Laws & Reaction Pathways <ul><li>A chemical reaction usually takes place in  several steps  as the molecules collide....
Reaction Mechanisms <ul><li>The series of steps  that actually occur  in a chemical reaction. </li></ul><ul><li>A balanced...
A Molecular Representation of the Elementary Steps in the Reaction of NO 2  and CO   Overall:  NO 2  + CO    NO + CO 2 St...
<ul><li>2NO 2  + F 2   2NO 2 F  </li></ul><ul><li>The  proposed  mechanism is: </li></ul><ul><li>NO 2  + F 2    NO 2 F  + ...
<ul><li>Each of the two reactions in the last slide is called an  elementary step . </li></ul><ul><li>The rate for each re...
<ul><li>2NO 2  + F 2   2NO 2 F    The  proposed  mechanism is:   NO 2  + F 2    NO 2 F  + F  (slow)  F  + NO 2    NO 2 F (...
<ul><li>Unimolecular  step involves one molecule - Rate is  first  order. </li></ul><ul><li>Bimolecular  step - requires t...
<ul><li>A  products </li></ul><ul><li>A+A  products </li></ul><ul><li>2A    products </li></ul><ul><li>A+B  products </li>...
Finding the Reaction Mechanism   <ul><li>Must satisfy  two  requirements: </li></ul><ul><li>Sum of the  elementary  steps ...
Review Problems   pp   <ul><li>A reaction of X & Y occurs by a 1-step mechanism:  X + 2Y     XY 2   </li></ul><ul><li>Wri...
Review Problems   pp   <ul><li>A reaction of X & Y occurs by a 1-step mechanism:  X + 2Y     XY 2   Rate = k[X][Y] 2   Wh...
Review Problems   pp   <ul><li>The rate of X reacting with Y doubles when [X] is doubled, but increases 8 times when [Y] i...
Review Problems   pp   <ul><li>The rate law for a  single-step  reaction that forms only one product, C, is  Rate = k[A] 2...
<ul><li>This reaction takes place in three steps </li></ul>
<ul><li>First step is fast </li></ul><ul><li>Low activation energy </li></ul>E a
Second step is slow High activation energy E a
E a Third step is fast Low activation energy
Second step is rate determining
Intermediates are present
Activated Complexes or Transition States
Mechanisms  and rates  <ul><li>There is an activation energy for  each  elementary step. </li></ul><ul><li>Slowest step  (...
Nuclear Review for Star Test
Types of Radiation <ul><li>Alpha particle (  ) </li></ul><ul><ul><li>helium nucleus </li></ul></ul>paper 2+ <ul><li>Beta ...
Nuclear Decay <ul><li>Alpha Emission </li></ul>Atomic & Mass Numbers must balance!! parent nuclide daughter nuclide alpha ...
Nuclear Decay <ul><li>Beta Emission </li></ul><ul><li>Positron Emission </li></ul>electron positron
Nuclear Decay <ul><li>Electron Capture  (of inner orbital electrons) </li></ul><ul><li>Gamma Emission </li></ul><ul><ul><l...
Learning Check <ul><li>Write the nuclear equation for the beta emitter Cobalt-60. . . </li></ul><ul><li>60 Co     60 Ni + ...
Learning Check NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>1...
 
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Ch17 hrw rxn kinetics

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  • Hrw 511
  • Hrw 531
  • Hrw 531; z53 Section 12.6 Reaction Mechanisms Z5e 583
  • Fig. 12.9 Z5e 584 NO 2 + NO 2 ---&gt; NO 3 + NO (k 1 ) NO 3 + CO ---&gt; NO 2 + CO 2 (k 2 ) NO 3 is an intermediate Each rx called an elementary step ; I.e., its rate law can be written from its molecularity Molecularity is defined as the # of species that must collide to produce the rxn indicated by that step.
  • Z5e 584
  • Z5e 585.
  • i.e., 3 moles of H 2 are being consumed for every 1 mole of N 2
  • Z5e Fig. 12.1 Definition of Rate Z5e 562
  • Hrw 532
  • Fig. 12.13 Z5e 589 (a) and (b) lead to a reaction, but (c) cannot.
  • Hrw 534
  • Hrw 534
  • Hrw 562-563
  • Vonderbrink PL 17
  • Hrw 705-707; z5e 1024-1025
  • Hrw 706; z5e 1024
  • Hrw 706; z5e 1024-1025
  • Hrw 707; z5e 1024-1025
  • Hrw 686; z5e 1083
  • Hrw 686
  • Hrw 538
  • Z5e 559
  • Hrw 538
  • Hrw 539
  • Hrw 539
  • Hrw 540
  • Hrw 540
  • Hrw 540 Section 12.8 Catalysis Z5e 592
  • Fig. 12.15 Z5e 593
  • Hrw 541
  • Hwr 541
  • Z5e 594
  • Z5e 598
  • Hrw 541 Section 12.2 Rate Laws Z5e 564 When fwd &amp; rev rxn rates are equal then no change in conc. of either --&gt; equilibrium Rate = k [H 2 ] m [NH 3 ] n Note: “m” and “n” are not coefficients of the balanced equation
  • Hrw 541
  • Hrw 541
  • “ n” is not the coefficient of the balanced reaction. Rf. Z5e 566
  • Z5e Fig. 12.1 Definition of Rate Z5e 562
  • Section 12.3 Determining the Form of the Rate Law Z5e 567
  • Z5e 568
  • Hrw 541-542 Z5e 570 SE 1.
  • Rf. SE 12.1 Z5e 570 Be able to write the rate law (using variables) from the reaction !
  • See SE 12.1 Z5e 570
  • See SE 12.1 Z5e 570
  • See SE 12.1 Z5e 570
  • See SE 12.1 Z5e 570
  • Hrw 542
  • Hrw 542 Z5e Section 12.6 Reaction Mechanisms Z5e 583
  • Hrw 542-543 Fig. 12.9 Z5e 584 NO 2 + NO 2 ---&gt; NO 3 + NO (k 1 ) NO 3 + CO ---&gt; NO 2 + CO 2 (k 2 ) NO 3 is an intermediate Each rx called an elementary step ; I.e., its rate law can be written from its molecularity Molecularity is defined as the # of species that must collide to produce the rxn indicated by that step.
  • See Hrw 544 SP 17-6
  • Z5e 584
  • See Hrw 544 SP 17-6
  • Rf. Table 12.7 Z5e 585
  • Z5e 585.
  • Hrw 544 SP 17-7
  • Hrw 544 SP 17-7
  • Hrw 544 Addl SP 17-7 #2
  • Hrw 544 Addl SP 17-7 #3
  • Hrw 705-707; z5e 1024-1025
  • Hrw 706; z5e 1024
  • Hrw 706; z5e 1024-1025
  • Hrw 707; z5e 1024-1025
  • Ch17 hrw rxn kinetics

    1. 1. Chapter 17 pp Reaction Kinetics
    2. 2. 17.1 The Reaction Process <ul><li>Explain the concept of reaction mechanism . </li></ul><ul><li>Use collision theory to interpret reactions. </li></ul><ul><li>Define activated complex . </li></ul><ul><li>Relate activation energy to heat of reaction. </li></ul>
    3. 3. Reaction Mechanisms <ul><li>The series of steps that actually occur in a chemical reaction. </li></ul><ul><li>A balanced equation does not tell us how the reactants become products. </li></ul><ul><li>Kinetics can tell us something about the mechanism. </li></ul>
    4. 4. A Molecular Representation of the Elementary Steps in the Reaction of NO 2 and CO Overall: NO 2 + CO  NO + CO 2 Step 1: NO 2 + NO 2  NO 3 + NO (k 1 ) Step 2: NO 3 + CO  NO 2 + CO 2 (k 2 ) NO 3 is an intermediate
    5. 5. <ul><li>2NO 2 + F 2 2NO 2 F </li></ul><ul><li>Rate = k[NO 2 ][F 2 ] </li></ul><ul><li>The proposed mechanism is: </li></ul><ul><li>NO 2 + F 2 NO 2 F + F (slow) </li></ul><ul><li>F + NO 2 NO 2 F (fast) </li></ul><ul><li>F is called an intermediate. It is formed then consumed in the reaction </li></ul>Reaction Mechanisms
    6. 6. <ul><li>Each of the two reactions is called an elementary step . </li></ul><ul><li>The rate for each reaction can be written from its molecularity . </li></ul><ul><li>Molecularity is the number of pieces that must come together ( collide ) to produce the reaction indicated by that step. </li></ul>Reaction Mechanisms
    7. 7. Finding the Reaction Mechanism <ul><li>Must satisfy two requirements : </li></ul><ul><li>1. Sum of the elementary steps does give the overall balanced equation for the reaction </li></ul><ul><li>2. The proposed mechanism must agree with the experimentally derived rate law. </li></ul>
    8. 8. <ul><li>N 2 + 3H 2 2NH 3 As the reaction progresses the concentration H 2 goes down </li></ul>Concentration Time [H 2 ]
    9. 9. <ul><li>As N 2 + 3H 2 2NH 3 progresses the concentration N 2 goes down 1/3 as fast </li></ul>Concentration Time [H 2 ] [N 2 ]
    10. 10. <ul><li>As N 2 + 3H 2 2NH 3 progresses the concentration NH 3 goes up. </li></ul>Concentration Time [H 2 ] [N 2 ] [NH 3 ]
    11. 11. Definition of Rate. 2NO 2  2NO + O 2
    12. 12. Collision Theory <ul><li>In order to react molecules and atoms must touch each other. </li></ul><ul><li>They must hit each other hard enough to react. </li></ul><ul><li>Anything that increases collision force will make the reaction faster . </li></ul><ul><li>They must also hit with the correct orientation or the collision won’t be “successful” & won’t cause a reaction. </li></ul><ul><li>LD 4: 17.35 Collisions & Rxn mechanisms </li></ul>
    13. 13. Tr96 Fig. 17-9 p. 533 Possible Collision Patterns
    14. 14. Several Possible Orientations for a Collision Between Two BrNO Molecules. (a) & (b) can lead to a collision, (c) cannot.
    15. 15. No Reaction O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br O N Br
    16. 16. Activation Energy <ul><li>Two things must happen for a reaction to occur. </li></ul><ul><li>Bonds must break within the reactants (requires energy). </li></ul><ul><li>Bonds must form to make products (gives off energy). </li></ul><ul><li>This process makes a temporary compound that last while new bonds are breaking and forming. </li></ul><ul><li>This is an activated complex . </li></ul>
    17. 17. Activation Energy <ul><li>Once an exothermic reaction gets started, the energy from bonds forming to make products is enough to sustain the reaction. </li></ul><ul><li>But, initially need energy to start the exothermic reaction. </li></ul><ul><li>Activation Energy - the minimum energy needed to transform the reactants into an activated complex. </li></ul>
    18. 18. Energy Reaction coordinate Reactants Products
    19. 19. Energy Reaction coordinate Reactants Products Activation Energy - Minimum energy to make the reaction happen
    20. 20. Energy Reaction coordinate Reactants Products Activated Complex or Transition State
    21. 21. Energy Reaction coordinate Reactants Products Overall energy change
    22. 22. Tr95A A e Differences in Exothermic & Endothermic Reactions <ul><li>How much bigger is E a (reverse) than E a (forward)? . . . </li></ul><ul><li>E a (reverse) = E a ( forward ) + ∆H rxn </li></ul><ul><li>What’s value of ∆H reverse rxn ? </li></ul><ul><li>∆ H reverse rxn = (+) 393 kJ </li></ul>
    23. 23. Tr95A A e Differences in Exothermic & Endothermic Reactions <ul><li>What are the products of the reverse reaction? . . . </li></ul><ul><li>2K (s) + 2H 2 O (l) </li></ul>
    24. 24. Detour for STAR Test review <ul><li>The following slides will review the important things you need to know for the STAR test. </li></ul><ul><li>You can also look at the chapters on equilibrium, nuclear chemistry, and organic chemistry. </li></ul>
    25. 25. Le Châtelier’s Principle <ul><li>If something is changed in a system at equilibrium, the system will respond to relieve the stress. </li></ul><ul><li>Three types of stress are applied: </li></ul><ul><ul><li>Pressure </li></ul></ul><ul><ul><li>Concentration </li></ul></ul><ul><ul><li>Temperature </li></ul></ul>
    26. 26. Changes in Pressure <ul><li>As the pressure increases the reaction will shift in the direction of the least gases. </li></ul><ul><li>At high pressure 2H 2 (g) + O 2 (g)  2 H 2 O(g) </li></ul><ul><li>At low pressure 2H 2 (g) + O 2 (g)  2 H 2 O(g) </li></ul>
    27. 27. Changing Concentration N 2(g) + 3H 2(g) 2NH 3(g) <ul><li>If you add reactants ( i.e. , increase their concentration) the forward reaction will speed up. </li></ul><ul><li>More product will form. </li></ul><ul><li>Equilibrium “ Shifts to the right ” </li></ul><ul><li>Reactants  products </li></ul>
    28. 28. Changing Concentration N 2(g) + 3H 2(g) 2NH 3(g) <ul><li>If you remove reactants (or decrease their concentration). </li></ul><ul><li>The reverse reaction will speed up. </li></ul><ul><li>More reactant will form. </li></ul><ul><li>Equilibrium “ Shifts to the left ”. </li></ul><ul><li>Reactants  products </li></ul><ul><li>Used to control how much yield you get from a chemical reaction. </li></ul>
    29. 29. Changing Concentration N 2(g) + 3H 2(g) 2NH 3(g) <ul><li>If you add products ( i.e. , increase their concentration). </li></ul><ul><li>The reverse reaction will speed up. </li></ul><ul><li>More reactant will form. </li></ul><ul><li>Equilibrium “ Shifts to the left ” </li></ul><ul><li>Reactants  products </li></ul>
    30. 30. Changing Concentration N 2(g) + 3H 2(g) 2NH 3(g) <ul><li>If you remove products (or decrease their concentration). </li></ul><ul><li>The forward reaction will speed up. </li></ul><ul><li>More product will form. </li></ul><ul><li>Equilibrium “ Shifts to the right ” </li></ul><ul><li>Reactants  products </li></ul>
    31. 31. Changing Temperature N 2(g) + 3H 2(g) 2NH 3(g) + 92 kJ <ul><li>Reactions either require or release heat. </li></ul><ul><li>Exothermic go faster at lower temperatures. </li></ul><ul><li>Endothermic reactions go faster at higher temperature. </li></ul><ul><li>All reversible reactions will be endothermic one way and exothermic the reverse way. </li></ul><ul><li>LD 3: 18.6 Reversible cobalt complex </li></ul>
    32. 32. Exothermic Review N 2(g) + 3H 2(g) 2NH 3(g) + 92 kJ <ul><li> H < 0 </li></ul><ul><li>Releases heat </li></ul><ul><li>Think of heat as a product in exo rxns </li></ul><ul><li>Raising temperature pushes toward reactants . </li></ul><ul><li>Shifts to left . </li></ul>
    33. 33. Endothermic Review 2H 2 O (g) + 484 kJ 2H 2(g) + O 2(g) <ul><li> H > 0 </li></ul><ul><li>Requires heat </li></ul><ul><li>Think of heat as a reactant </li></ul><ul><li>Raising temperature push toward products . </li></ul><ul><li>Shifts to right . </li></ul>
    34. 34. Gas Phase Equilibrium <ul><li> catalyst N 2(g) + 3 H 2(g) 2 NH 3(g) + heat high pressure and temperature </li></ul><ul><li>Endothermic or exothermic? . . . </li></ul><ul><li>Exothermic. </li></ul><ul><li>Adding heat shifts which way? </li></ul><ul><li>Left </li></ul><ul><li>Cooling the system shifts which way? </li></ul><ul><li>Right </li></ul>
    35. 35. Le Chatelier Review pp <ul><li>6CO 2(g) + 6H 2 O (l) C 6 H 12 O 6(s) + 6O 2(g) ∆H = 2820 kJ </li></ul><ul><li>Some CO 2(g) is added and causes . . . </li></ul><ul><li>Shift to right so get more C 6 H 12 O 6(s) . </li></ul><ul><li>Temperature is raised . . . </li></ul><ul><li>Shift to right, more C 6 H 12 O 6(s) forms. </li></ul><ul><li>Volume is decreased </li></ul><ul><li>There are equal moles of gaseous reactants and products, so no change. </li></ul>
    36. 36. Le Chatelier Review pp <ul><li>6CO 2(g) + 6H 2 O (l) C 6 H 12 O 6(s) + 6O 2(g) ∆H = 2820 kJ </li></ul><ul><li>Some O 2(g) is removed . . . </li></ul><ul><li>Shift to right, more C 6 H 12 O 6(s) forms. </li></ul><ul><li>Some C 6 H 12 O 6(s) is removed . . . </li></ul><ul><li>No change (glucose is a solid so is not in the equilibrium expression). No more C 6 H 12 O 6(s) . </li></ul><ul><li>A catalyst is added . . . </li></ul><ul><li>No effect on equilibrium, only allows it be attained more quickly. No more C 6 H 12 O 6(s) . </li></ul>
    37. 37. Le Chatelier Review pp <ul><li>6CO 2(g) + 6H 2 O (l) C 6 H 12 O 6(s) + 6O 2(g) ∆H = 2820 kJ </li></ul><ul><li>Some H 2 O is removed . . . </li></ul><ul><li>No change, water is a liquid. No additional C 6 H 12 O 6(s) forms. </li></ul>
    38. 38. Radiation <ul><li>Radiation comes from the nucleus of an atom. </li></ul><ul><li>Unstable nucleus emits a particle or energy  alpha </li></ul><ul><li>  beta </li></ul><ul><li>  gamma </li></ul>
    39. 39. A. Types of Radiation pp <ul><li>Alpha particle (  ) </li></ul><ul><ul><li>helium nucleus </li></ul></ul>paper 2+ <ul><li>Beta particle (  -) </li></ul><ul><ul><li>electron </li></ul></ul>1- lead <ul><li>Positron (  +) </li></ul><ul><ul><li>positron </li></ul></ul>1+ <ul><li>Gamma (  ) </li></ul><ul><ul><li>high-energy photon </li></ul></ul>0 concrete
    40. 40. Radiation Protection <ul><li>Shielding </li></ul><ul><li>alpha – paper, clothing </li></ul><ul><li>beta – lab coat, gloves </li></ul><ul><li>gamma- lead, thick concrete </li></ul><ul><li>Limit time exposed </li></ul><ul><li>Keep distance from source </li></ul>
    41. 41. Radiation Protection
    42. 42. B. Nuclear Decay pp <ul><li>Alpha Emission </li></ul>Atomic & Mass Numbers must balance!! parent nuclide daughter nuclide alpha particle
    43. 43. B. Nuclear Decay pp <ul><li>Beta Emission </li></ul><ul><li>Positron Emission </li></ul>electron positron
    44. 44. B. Nuclear Decay pp <ul><li>Electron Capture </li></ul><ul><li>Gamma Emission </li></ul><ul><ul><li>Usually follows other types of decay. </li></ul></ul><ul><li>Transmutation </li></ul><ul><ul><li>One element becomes another. </li></ul></ul>electron
    45. 46. Gamma radiation pp <ul><li>No change in atomic or mass number </li></ul><ul><li>11 B 11 B + 0  </li></ul><ul><li>5 5 0 </li></ul><ul><li>boron atom in a </li></ul><ul><li>high-energy state </li></ul>
    46. 48. Learning Check NR1 pp <ul><li>Write the nuclear equation for the beta emitter Cobalt-60. . . </li></ul>
    47. 49. Solution NR1 pp <ul><li>Write the nuclear equation for the </li></ul><ul><li>Beta emitter Cobalt-60. </li></ul><ul><li>60 Co 60 Ni + 0 e </li></ul><ul><li>27 28 -1 </li></ul>
    48. 50. Producing Radioactive Isotopes <ul><li>Bombardment of atoms produces radioisotopes </li></ul><ul><li> = 60 = 60 </li></ul><ul><li>59 Co + 1 n 56 Mn + 4 H e </li></ul><ul><li>27 0 25 2 </li></ul><ul><li> = 27 = 27 </li></ul><ul><li>cobalt neutron manganese alpha </li></ul><ul><li>atom radioisotope particle </li></ul>
    49. 51. Learning Check NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>10 B + 4 He ? + 1 n </li></ul><ul><li>5 2 0 </li></ul>
    50. 52. Solution NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>10 B + 4 He 13 N + 1 n </li></ul><ul><li>5 2 7 0 </li></ul><ul><li> nitrogen </li></ul><ul><li> radioisotope </li></ul>
    51. 53. Addition Polymers pp <ul><li>Polymers are giant molecules, not small like the ones studied earlier in this chapter </li></ul><ul><li>Examples are plastics </li></ul><ul><li>Polymer - large molecule formed by the covalent bonding of smaller molecules called monomers </li></ul>
    52. 54. Addition Polymers
    53. 55. 17.2 Reaction Rate <ul><li>Define chemical kinetics & explain the 2 conditions necessary for chemical reactions to occur. </li></ul><ul><li>Discuss the 5 factors influencing rate. </li></ul><ul><li>Define catalyst and discuss 2 types. </li></ul><ul><li>Explain & write rate laws for chemical reactions. </li></ul>
    54. 56. Kinetics <ul><li>The study of reaction rates. </li></ul><ul><li>Spontaneous reactions are reactions that will happen - but we can’t tell how fast. </li></ul><ul><li>Diamond will spontaneously turn to graphite – eventually. </li></ul><ul><li>Reaction mechanism - the steps by which a reaction takes place. </li></ul>
    55. 57. Things that Affect Rate #1 Nature of Reactants <ul><li>Different substances have different reactivities. </li></ul><ul><li>Hydrogen reacts vigorously with chlorine, but only feebly with nitrogen. </li></ul><ul><li>The rate depends on the particular reactants and bonds involved. </li></ul>
    56. 58. Things that Affect Rate #2 Surface Area <ul><li>Particle size determines surface area. </li></ul><ul><li>Molecules can only collide at the surface . </li></ul><ul><li>Smaller particles have bigger surface area. </li></ul><ul><li>So, smaller particles have faster reaction. </li></ul><ul><li>Smallest possible is molecules or ions. </li></ul><ul><li>Dissolving speeds up reactions since the particle size gets smaller. </li></ul><ul><li>Getting two solids to react with each other is slow (big particle size). </li></ul><ul><li>LD 4:17.42 Lycopodium </li></ul>
    57. 59. Things that Affect Rate #3 Temperature <ul><li>Higher temperature - faster particles. </li></ul><ul><li>Greater kinetic energy. </li></ul><ul><li>More and stronger collisions. </li></ul><ul><li>So, get faster Reactions. </li></ul><ul><li>Decreasing temperature has opposite effect. </li></ul><ul><li>Rule of thumb: Beginning at room temperature (25 ºC), rate doubles with each 10 ºC rise in temperature. </li></ul><ul><li>Rules of thumb always have exceptions. </li></ul><ul><li>LD 4: 17.45 Bleaching dye hot/cold water. </li></ul>
    58. 60. Things that Affect Rate #4 Concentration <ul><li>More concentrated means the molecules are closer together. </li></ul><ul><li>So, they collide more often. </li></ul><ul><li>Get a faster reaction. </li></ul><ul><li>LD 4:46 Mg + HCl, different concentrations. </li></ul>
    59. 61. Tr98 Fig. 17-13 p. 540 Concentration Affects Rate <ul><li>How many collisions can occur between 6 “A” particles & 4 “B” particles? . . . </li></ul><ul><li>24 collisions. </li></ul>
    60. 62. Things that Affect Rate #5 Catalysts <ul><li>Substances that speed up a reaction without being used up ( e.g., enzyme). </li></ul><ul><li>LD 4: 17.50 H 2 O 2 catalytic decomposition. </li></ul><ul><li>Speeds up reaction by giving the reaction a new path . </li></ul><ul><li>New path has a lower activation energy. </li></ul><ul><li>Since more molecules have this energy the reaction goes faster. </li></ul><ul><li>Inhibitor - a substance that blocks a catalyst. </li></ul>
    61. 63. Energy Reaction coordinate Reactants Products
    62. 64. Catalysts <ul><li>Speed up a reaction without being used up in the reaction. </li></ul><ul><li>Enzymes are biological catalysts. </li></ul><ul><li>Homogenous Catalysts are in the same phase as the reactants. </li></ul><ul><li>Heterogeneous Catalysts are in a different phase as the reactants. </li></ul>
    63. 65. Energy Plots for a Catalyzed and an Uncatalyzed Pathway for a Given Reaction. ∆ E is the same in both cases!
    64. 66. Tr97A Fig. 17-15 p. 541 Comparing Pathways for Decomposing H 2 O 2 by Various Catalysts <ul><li>Why is H 2 O 2 stored in brown bottles to protect it from UV light? </li></ul><ul><li>UV light has enough energy to catalyze the reaction. </li></ul>
    65. 67. Tr97A Fig. 17-15 p. 541 Comparing Pathways for Decomposing H 2 O 2 by Various Catalysts <ul><li>How many activated complexes are created with the heterogenous catalyst, MnO 2 ? . . . </li></ul><ul><li>There are 3 activated complexes. </li></ul>
    66. 68. <ul><li>Hydrogen bonds to surface of metal. </li></ul><ul><li>Break H-H bonds </li></ul>Catalysts Pt surface H H H H H H H H
    67. 69. Catalysts Pt surface H H H H C H H C H H
    68. 70. Catalysts <ul><li>The double bond breaks and bonds to the catalyst. </li></ul>Pt surface H H H H C H H C H H
    69. 71. Catalysts <ul><li>The hydrogen atoms bond with the carbon </li></ul>Pt surface H H H H C H H C H H
    70. 72. Catalysts Pt surface H C H H C H H H H H
    71. 73. Heterogenous Catalysts <ul><li>Summary: usually in 4 steps: </li></ul><ul><li>Adsorption & activation of reactants onto the catalytic surface. </li></ul><ul><li>Migration of the adsorbed reactants across the surface. </li></ul><ul><li>Reaction of the adsorbed reactants. </li></ul><ul><li>Escape (desorption) of the products . </li></ul>
    72. 74. Homogenous Catalysts <ul><li>Chlorofluorocarbons catalyze the decomposition of ozone. </li></ul><ul><li>Both are in same phase (gas) </li></ul><ul><li>Another example: Enzymes regulating the body processes. (Protein catalysts) </li></ul>
    73. 75. Catalysts and rate <ul><li>Catalysts will speed up a reaction but only to a certain point . </li></ul><ul><li>Past a certain point adding more reactants won’t change the rate. </li></ul><ul><li>Becomes Zero Order (saturation kinetics) </li></ul><ul><li>See saturation kinetics with renal disease & some drugs (aminoglycosides). </li></ul>
    74. 76. Catalysts and rate. <ul><li>Rate increases until the active sites of catalyst are filled. </li></ul><ul><li>Then rate is independent of concentration </li></ul>Concentration of reactants Rate
    75. 77. Rate Laws: An Introduction <ul><li>Reactions are reversible. </li></ul><ul><li>As products accumulate they can begin to turn back into reactants. </li></ul><ul><li>Early on the rate will depend on only the amount of reactants present. </li></ul><ul><li>So, we want to measure the reactants as soon as they are mixed . </li></ul><ul><li>This is called the Initial rate method . </li></ul>
    76. 78. <ul><li>Two key points </li></ul><ul><li>The concentration of the products do not appear in the rate law because this is an initial rate (only the [reactants]). </li></ul><ul><li>The order must be determined experimentally . </li></ul><ul><li>Can’t be obtained from the equation’s coefficients (unless it is single step - more later on this). </li></ul>Rate Laws
    77. 79. Rate Laws <ul><li>N 2 + 3H 2 2NH 3 </li></ul><ul><li>When forward & reverse reaction rates are equal then there is no change in concentration of either. </li></ul><ul><li>It’s at equilibrium. </li></ul><ul><li>Rate = k [N 2 ] n [H 2 ] m </li></ul><ul><li>Note: “m” and “n” are not coefficients of the balanced equation (unless single step), must be determined experimentally. </li></ul>
    78. 80. <ul><li>You will find that the rate will only depend on the concentration of the reactants . </li></ul><ul><li>Rate = k [NO 2 ] n </li></ul><ul><li>This is called a rate law expression . </li></ul><ul><li>k is called the rate constant. </li></ul><ul><li>n is the order of the reactant - usually a positive integer (1st, 2nd, etc.). </li></ul>2 NO 2 2 NO + O 2
    79. 81. Definition of Rate. 2NO 2  2NO + O 2
    80. 82. Determining Rate Laws <ul><li>The first step is to determine the form of the rate law (especially its order ). </li></ul><ul><li>Must be determined from experimental data ( not from the coefficients!!). </li></ul><ul><li>You’ll do this type of lab in AP Chem. </li></ul>
    81. 83. The method of Initial Rates <ul><li>This method requires that a reaction be run several times (do in AP Chem). </li></ul><ul><li>The initial concentrations of the reactants are varied. </li></ul><ul><li>The reaction rate is measured just after the reactants are mixed. </li></ul><ul><li>Eliminates the effect of the reverse reaction and makes easier to calculate. </li></ul>
    82. 84. Rate Law Example pp <ul><li>Write the general form of rate law for: BrO 3 - + 5 Br - + 6H + 3Br 2 + 3 H 2 O </li></ul><ul><li>Answer is . . . </li></ul><ul><li>Rate = k [BrO 3 - ] n [Br - ] m [H + ] p </li></ul><ul><li>Determine n , m , p by comparing rates </li></ul><ul><li>Add n , m , p values to get overall order </li></ul>
    83. 85. Example Continued pp <ul><li>So, for the reaction BrO 3 - + 5 Br - + 6H + 3Br 2 + 3 H 2 O The general form of the Rate Law is Rate = k[BrO 3 - ] n [Br - ] m [H + ] p </li></ul><ul><li>Be able to write this as the the answer to a question, given the above reaction). </li></ul><ul><li>We use experimental data to determine the values of n,m, and p </li></ul>
    84. 86. <ul><li>Now we have to see how the rate changes with concentration </li></ul>Initial concentrations (M) pp Rate (M/s) BrO 3 - Br - H + 0.10 0.10 0.10 8.0 x 10 -4 0.20 0.10 0.10 1.6 x 10 -3 0.20 0.20 0.10 3.2 x 10 -3 0.10 0.10 0.20 3.2 x 10 -3
    85. 87. <ul><li>Find n by ratio of Rate 2/Rate 1, in which only [BrO 3 - ] changes </li></ul><ul><li>n = 1 because (next slide) </li></ul>Initial concentrations ( M ) pp Rate (M/s) BrO 3 - Br - H + 0.10 0.10 0.10 8.0 x 10 -4 0.20 0.10 0.10 1.6 x 10 -3 0.20 0.20 0.10 3.2 x 10 -3 0.10 0.10 0.20 3.2 x 10 -3
    86. 88. The math pp <ul><li>Rate 2 = 1 .6 x 10 -3 mol/Ls = k(0.20 mol/L) n (0.10 mol/l) m (0.10 mol/L) p Rate 1 8.0 x 10 -4 mol/Ls k(0.10 mol/L) n (0.10 mol/l) m (0.10 mol/L) p </li></ul><ul><li>= 2.0 = (0.20 mol/L / 0.10 mol/L) n = (2.0) n </li></ul><ul><li>So, n = 1 </li></ul><ul><li>Easy way: when the concentration was doubled the rate was doubled so n = 1. </li></ul><ul><li>This is the “take-home” message for you. </li></ul>
    87. 89. <ul><li>Find m by ratio of Rate 3/Rate 2, in which only [Br - ] changes </li></ul><ul><li>m = 1 (ditto on math) </li></ul>Initial concentrations ( M ) pp Rate (M/s) BrO 3 - Br - H + 0.10 0.10 0.10 8.0 x 10 -4 0.20 0.10 0.10 1.6 x 10 -3 0.20 0.20 0.10 3.2 x 10 -3 0.10 0.10 0.20 3.2 x 10 -3
    88. 90. <ul><li>Find p by ratio of Rate 4/Rate 1, in which only [H + ] changes </li></ul><ul><li>p = 2 (next slide) </li></ul>Initial concentrations ( M ) pp Rate (M/s) BrO 3 - Br - H + 0.10 0.10 0.10 8.0 x 10 -4 0.20 0.10 0.10 1.6 x 10 -3 0.20 0.20 0.10 3.2 x 10 -3 0.10 0.10 0.20 3.2 x 10 -3
    89. 91. <ul><li>When double [H 1+ ] the rate quadruples so p = 2 </li></ul><ul><li>Double : quadruple = 2 : 4 = 2 : 2 2 </li></ul>Initial concentrations ( M ) pp Rate (M/s) BrO 3 - Br - H + 0.10 0.10 0.10 8.0 x 10 -4 0.20 0.10 0.10 1.6 x 10 -3 0.20 0.20 0.10 3.2 x 10 -3 0.10 0.10 0.20 3.2 x 10 -3
    90. 92. Example continued pp <ul><li>So, rate of reaction is first order in BrO 3 - and Br - and second order in H + </li></ul><ul><li>Overall rate = 1 + 1 + 2 = 4 </li></ul><ul><li>Rate law can be written as: </li></ul><ul><li>Rate = k [BrO 3 - ][Br - ][H + ] 2 </li></ul>
    91. 93. Rate Laws & Reaction Pathways <ul><li>A chemical reaction usually takes place in several steps as the molecules collide. </li></ul><ul><li>Elementary reaction - a reaction that happens in a single step </li></ul><ul><li>Reaction mechanism is a description of how the chemical reaction really happens. </li></ul><ul><li>It is a series of elementary reactions . </li></ul><ul><li>The product of an elementary reaction is an intermediate . </li></ul><ul><li>An intermediate is a product that immediately gets used in the next reaction. </li></ul>
    92. 94. Reaction Mechanisms <ul><li>The series of steps that actually occur in a chemical reaction. </li></ul><ul><li>A balanced equation does not tell us how the reactants become products. </li></ul><ul><li>Kinetics can tell us something about the mechanism. </li></ul>
    93. 95. A Molecular Representation of the Elementary Steps in the Reaction of NO 2 and CO Overall: NO 2 + CO  NO + CO 2 Step 1: NO 2 + NO 2  NO 3 + NO (k 1 ) Step 2: NO 3 + CO  NO 2 + CO 2 (k 2 ) NO 3 is an intermediate
    94. 96. <ul><li>2NO 2 + F 2 2NO 2 F </li></ul><ul><li>The proposed mechanism is: </li></ul><ul><li>NO 2 + F 2 NO 2 F + F (slow) </li></ul><ul><li>F + NO 2 NO 2 F (fast) </li></ul><ul><li>F is called an intermediate. It is formed then consumed in the reaction. </li></ul><ul><li>Both steps are “elementary” steps. </li></ul>Reaction Mechanisms pp
    95. 97. <ul><li>Each of the two reactions in the last slide is called an elementary step . </li></ul><ul><li>The rate for each reaction can be written from its molecularity . </li></ul><ul><li>Molecularity is the number of pieces that must come together (collide) to produce the reaction indicated by that step. </li></ul>Reaction Mechanisms
    96. 98. <ul><li>2NO 2 + F 2 2NO 2 F The proposed mechanism is: NO 2 + F 2 NO 2 F + F (slow) F + NO 2 NO 2 F (fast) F is called an intermediate. It is formed then consumed in the reaction. Both steps are “elementary” steps. </li></ul><ul><li>Since the first one is slow & elementary it is rate-determining. </li></ul><ul><li>So, Rate = k[ NO 2 ][ F 2 ] </li></ul>Reaction Mechanisms
    97. 99. <ul><li>Unimolecular step involves one molecule - Rate is first order. </li></ul><ul><li>Bimolecular step - requires two molecules - Rate is second order </li></ul><ul><li>Termolecular step - requires three molecules - Rate is third order </li></ul><ul><li>Termolecular steps are almost never heard of because the chances of three molecules coming into contact at the same time are miniscule. </li></ul><ul><li>With molecularity the coefficients can become the exponents. </li></ul>
    98. 100. <ul><li>A products </li></ul><ul><li>A+A products </li></ul><ul><li>2A products </li></ul><ul><li>A+B products </li></ul><ul><li>A+A+B Products </li></ul><ul><li>2A+B Products </li></ul><ul><li>A+B+C Products </li></ul><ul><li>Rate = k[A] </li></ul><ul><li>Rate= k[A] 2 </li></ul><ul><li>Rate= k[A] 2 </li></ul><ul><li>Rate= k[A][B] </li></ul><ul><li>Rate= k[A] 2 [B] </li></ul><ul><li>Rate= k[A] 2 [B] </li></ul><ul><li>Rate= k[A][B][C] </li></ul>
    99. 101. Finding the Reaction Mechanism <ul><li>Must satisfy two requirements: </li></ul><ul><li>Sum of the elementary steps does give the overall balanced equation for the reaction </li></ul><ul><li>The proposed mechanism must agree with the experimentally derived rate law. </li></ul>
    100. 102. Review Problems pp <ul><li>A reaction of X & Y occurs by a 1-step mechanism: X + 2Y  XY 2 </li></ul><ul><li>Write the rate law . . . </li></ul><ul><li>Rate = k[X][Y] 2 </li></ul><ul><li>What happens to rate if double [X]? . . . </li></ul><ul><li>Rate is doubled (1st order in X) </li></ul><ul><li>If double [Y]? . . . </li></ul><ul><li>Rate is quadrupled (2nd order in Y) </li></ul>
    101. 103. Review Problems pp <ul><li>A reaction of X & Y occurs by a 1-step mechanism: X + 2Y  XY 2 Rate = k[X][Y] 2 What happens to the rate if only use 1/3 of Y? . . . </li></ul><ul><li>Rate is 1/9 the original because . . . </li></ul><ul><li>2 nd order in Y so (1/3) 2 = 1/9 </li></ul>
    102. 104. Review Problems pp <ul><li>The rate of X reacting with Y doubles when [X] is doubled, but increases 8 times when [Y] is doubled. Write the rate law . . . </li></ul><ul><li>Rate = k[X][Y] 3 because . . . </li></ul><ul><li>Double:double = 2:2 1 so “n” = 1 , 1st order </li></ul><ul><li>Double:8 times = 2:2 3 so “m”= 3 , 3rd order. </li></ul>
    103. 105. Review Problems pp <ul><li>The rate law for a single-step reaction that forms only one product, C, is Rate = k[A] 2 [B] Write the balanced equation . . . </li></ul><ul><li>2A + B  C </li></ul>
    104. 106. <ul><li>This reaction takes place in three steps </li></ul>
    105. 107. <ul><li>First step is fast </li></ul><ul><li>Low activation energy </li></ul>E a
    106. 108. Second step is slow High activation energy E a
    107. 109. E a Third step is fast Low activation energy
    108. 110. Second step is rate determining
    109. 111. Intermediates are present
    110. 112. Activated Complexes or Transition States
    111. 113. Mechanisms and rates <ul><li>There is an activation energy for each elementary step. </li></ul><ul><li>Slowest step (rate determining) must have the highest activation energy. </li></ul>
    112. 114. Nuclear Review for Star Test
    113. 115. Types of Radiation <ul><li>Alpha particle (  ) </li></ul><ul><ul><li>helium nucleus </li></ul></ul>paper 2+ <ul><li>Beta particle (  -) </li></ul><ul><ul><li>electron </li></ul></ul>1- lead <ul><li>Positron (  +) </li></ul><ul><ul><li>positron </li></ul></ul>1+ <ul><li>Gamma (  ) </li></ul><ul><ul><li>high-energy photon </li></ul></ul>0 concrete
    114. 116. Nuclear Decay <ul><li>Alpha Emission </li></ul>Atomic & Mass Numbers must balance!! parent nuclide daughter nuclide alpha particle
    115. 117. Nuclear Decay <ul><li>Beta Emission </li></ul><ul><li>Positron Emission </li></ul>electron positron
    116. 118. Nuclear Decay <ul><li>Electron Capture (of inner orbital electrons) </li></ul><ul><li>Gamma Emission </li></ul><ul><ul><li>Usually follows other types of decay. </li></ul></ul><ul><li>Transmutation </li></ul><ul><ul><li>One element becomes another. </li></ul></ul>electron
    117. 119. Learning Check <ul><li>Write the nuclear equation for the beta emitter Cobalt-60. . . </li></ul><ul><li>60 Co 60 Ni + 0 e 27 28 -1 </li></ul>
    118. 120. Learning Check NR2 <ul><li>What radioactive isotope is produced in the following bombardment of boron? </li></ul><ul><li>10 B + 4 He ? + 1 n </li></ul><ul><li>5 2 0 </li></ul>

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