1. Collision Theory Reaction Rates

2. Collision Theory
1) Atoms, ions, and molecules must collide in order to react. H I
No Reaction

3. Collision Theory
2) Reacting substances must collide with the correct orientation. H I
No Reaction

4. Collision Theory No Reaction
3) Reacting substances must collide with enough energy to form the activated complex. H I
No Reaction

5. Collision Theory
3) Reacting substances must collide with enough energy to form the activated complex. H H I I H I

6. Collision Theory
1) Atoms, ions, and molecules must collide in order to react.
2) Reacting substances must collide with the correct orientation.
3) Reacting substances must collide with enough energy to form the activated complex.

7. Activated Complex
A temporary, unstable arrangement of atoms that may form products or reactants.

8. Activation Energy (Ea)
Minimum amount of energy needed in a collision to form the activated complex.

9. Expressing Reaction Rates
Some chemical reactions are very fast and others are very slow.
To express the rate in clearer terms:
Average rate= ∆concentration ∆time

10. Calculating Reaction Rates
Use the table to determine the formation rate of NO(g):
CO(g) + NO2(g) → CO2(g) + NO(g)
0.0s
2.0s
0.000 M NO
0.010 M NO
0.005 mol/L*s
0.005
mol/L⦁s
t2 – t1
t2 – t1
rate =

11. Reaction Rates Example
Using the data table, calculate the average reaction rate over the time period expressed as moles of C4H9Cl consumed per liter per second.
Molarity of C4H9Cl
0.00s
4.00s
0.220M
0.100M

12. Comparing Reaction Rates
Using stoichiometry, we can compare the rates of two species in a reaction.
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
If C3H8 is decreasing at a rate of 2.00 M/s, at what rate is CO2 being produced?
-2.00 mol C3H8
3 mol CO2
6.00 mol CO2
L⦁s
-1 mol C3H8

13. Discussion Questions
1) What criteria must be met for reactant collisions to result in a successful product?
The reactants must collide with each other
The reactants must collide with enough energy and be in the right positions
The reactants must have enough energy to form the activated complex B

14. Discussion Questions
2) The most common way of expressing a reaction rate is in terms of:
mol/L
g/L⦁s
mol/L⦁s
mol/s C

15. Discussion Questions
3) What is the average rate of formation of salt in the first 10 seconds of this reaction?
HCl + NaOH → H2O + NaCl
0.287 mol/L*s
0.00 M NaCl at 0.00 s
2.87 M NaCl at s

16. Discussion Questions
4) What is the average rate of formation of CO2 between 3.00 and 7.00 seconds of this reaction?
H2CO3→ H2O + CO2
0.585 mol/L*s
1.08 M CO2 at 3.00 s
3.42 M CO2 at 7.00 s

17. Concentration (M of H2SO4) Reaction Time (seconds)
Discussion Questions
5) Use the table to determine the average rate of sulfuric acid being consumed in this reaction between 4 and 8 seconds.
2Fe + 3H2SO4→ 3H2 + Fe2(SO4)3
Concentration (M of H2SO4)
Reaction Time (seconds)
1.00
0.00
0.110
2.00
0.0625
4.00
0.0278
6.00
0.0156
8.00
0.0100
10.00
mol/L*s

18. Discussion Questions
6) As a reaction proceeds, the concentration of reactants will _______ and the concentration of products will ________.
increase, decrease
increase, increase
decrease, decrease
decrease, increase D

19. Discussion Questions
7) Calculate the rate of formation of iron(II) sulfide if sulfur is being consumed at a rate of mol/L⦁s. 8 Fe(s) + S8(s) → 8 FeS(s)
3.52 mol/L*s

20. Discussion Questions
8) Calculate the rate of formation of aluminum oxide if oxygen is being consumed at a rate of mol/L⦁s. 3 O2(g) + 4Al(s) → 2 Al2O3(s)
0.040 mol/L*s

21. Discussion Questions
9) At what rate is aluminum being consumed if aluminum oxide is being formed at 2.50 mol/L⦁s. 3 O2(g) + 4Al(s) → 2 Al2O3(s)
5.00 mol/L*s

22. Discussion Questions
10) At what rate is nitrogen being consumed if hydrogen is being consumed at mol/L⦁s. 3 H2(g) + N2(g) → 2 NH3(g)
mol/L*s