File:Ql2817-10.png

2019-05-16T15:29:32Z

Ql2817:

File:Ql2817-09.png

2019-05-16T15:29:18Z

Ql2817:

MRD:ql2817

2019-05-16T15:21:22Z

Ql2817: /* In light of the fact that energy is conserved, discuss the mechanism of release of the reaction energy. Explain how this could be confirmed experimentally. */

== '''Question 1''' ==

=== On a potential energy surface diagram, how is the transition state mathematically defined? How can the transition state be identified, and how can it be distinguished from a local minimum of the potential energy surface?===

The transition state is defined as the maximum on the minimum energy path linking reactants and the products.It is located at the saddle point in the potential energy surface diagram, which defined as : ∂V(ri)/∂ri=0 and H < 0, where H = frr(r0,V0)fVV(r0,V0)−f2rV(r0,V0) .

The transition state is the specific combination of internuclear distances AB and BC at which the trajectory is a point on the contour plot.

=== Report your best estimate of the transition state position (rts) and explain your reasoning illustrating it with a “Internuclear Distances vs Time” plot for a relevant trajectory. ===
When r(AB)=r(BC)=0.907 Å, p1 = p2 = 0.0, the transition state occurs. The internuclear distance vs time graph gives a relatively straight line which indicates a constant distance.

=== Comment on how the mep and the trajectory you just calculated differ. ===
The mep trajectory keeps the potential energy at the minimum in a straight line, whereas the dynamic trajectory is wavy.

r1 = 0.907, r2 = 0.917

Molecules and atome moving away from each other.

Setup a calculation where the initial positions correspond to the final positions of the trajectory you calculated above, the same final momenta values but with their signs reversed.

r1 = rts+δ, r2 = rts

final values of the positions r1(t) = 3.45, r2(t) = 0.72 and the average momenta p1(t) = -1.45, p2(t) = -2.48 at large t.

The molecule and the atom moving close together instead of moving apart.

=== Complete the table above by adding the total energy, whether the trajectory is reactive or unreactive, and provide a plot of the trajectory and a small description for what happens along the trajectory. What can you conclude from the table? ===

{| class="wikitable" border="5"
! P1!!P2 !! Etot!! Reactive?!!Description of the dyanmics!!Illustration of the trajectory
|-
| -1.25 || -2.5|| -99.08|| yes||The trajectory goes through the transition state and also go into the products. ||[[File:Surface01_ql2817.png]]
|-
| -1.5|| -2.0|| -100.22|| no||The trajectory falls back down into the reactants because there was not enough energy for reactants to pass over the transition state. || [[File:Surface02_ql2817.png]]
|-
| -1.5|| -2.5|| -98.91|| yes||The trajectory goes through the transition state and also go into the products with enough energy. || [[File:Surface03_ql2817.png]]
|-
| -2.5|| -5.0|| -84.62|| no||The trajectory was carrying enough energy towards products but then it shifts back into the reactants. || [[File:Surface04_ql2817.png]]
|-
| -2.5|| -5.2|| -83.40|| yes||The trajectory goes through the transition state and also go into the products with enough energy. || [[File:Surface05_ql2817.png]]
|}

=== State what are the main assumptions of Transition State Theory. Given the results you have obtained, how will Transition State Theory predictions for reaction rate values compare with experimental values? ===
Assumptions <ref name="main">https://en.wikibooks.org/wiki/Statistical_Thermodynamics_and_Rate_Theories/Eyring_Transition_State_Theory#Assumptions_of_Transition_State_Theory
</ref>

*Reactants are in constant equilibrium with the transition state structure.
*The energy of the particles follow a Boltzmann distribution.
*Once reactants become the transition state, the transition state structure does not collapse back to the reactants.

Transition state theory will predict a higher reaction rate than experimental one.

== '''Exercise 2: F-H-H system''' ==

===By inspecting the potential energy surfaces, classify the F + H2 and H + HF reactions according to their energetics (endothermic or exothermic). How does this relate to the bond strength of the chemical species involved? ===
'''F+H2:'''

r(AB)=1.5,r(BC)=0.74, AB,BC m=0

[[File:ql2817-01.png]]

exothermic, because the trajectory goes from a higher PE to a lower PE.

'''H+F2:'''

r(AB)=1.5,r(BC)=0.74, AB,BC m=0

[[File:ql2817-02.png]]

endothermic, because the trajectory goes from a lower PE to a higher PE.

===Locate the approximate position of the transition state. ===
'''F+H2:'''

r(AB): 1.8108
r(BC): 0.744877
AB BC m: 0

[[File:ql2817-03.png]]

'''H+HF:'''

r(AB): 0.744877
r(BC): 1.8108
AB BC m: 0

[[File:ql2817-04.png]]

===Report the activation energy for both reactions. ===
'''F+H2:'''

activation energy: 30 kcal/mol

[[File:ql2817-05.png]]

'''H+FH::'''

activation energy: 0.44kcal/mol

[[File:ql2817-06.png]]

=== In light of the fact that energy is conserved, discuss the mechanism of release of the reaction energy. Explain how this could be confirmed experimentally.===

reactive trajectory:

r(AB):1.6, r(BC):0.74, P AB:-0.5, P BC:0

[[File:ql2817-07.png]]

[[File:ql2817-08.png]]

===Discuss how the distribution of energy between different modes (translation and vibration) affect the efficiency of the reaction, and how this is influenced by the position of the transition state. ===

=='''References'''==
<references/>:

File:Ql2817-08.png

2019-05-16T15:18:21Z

Ql2817:

2019-05-16T13:51:35Z

Ql2817: /* Exercise 2: F-H-H system */

== '''Question 1''' ==

=== On a potential energy surface diagram, how is the transition state mathematically defined? How can the transition state be identified, and how can it be distinguished from a local minimum of the potential energy surface?===

The transition state is defined as the maximum on the minimum energy path linking reactants and the products.It is located at the saddle point in the potential energy surface diagram, which defined as : ∂V(ri)/∂ri=0 and H < 0, where H = frr(r0,V0)fVV(r0,V0)−f2rV(r0,V0) .

The transition state is the specific combination of internuclear distances AB and BC at which the trajectory is a point on the contour plot.

=== Report your best estimate of the transition state position (rts) and explain your reasoning illustrating it with a “Internuclear Distances vs Time” plot for a relevant trajectory. ===
When r(AB)=r(BC)=0.907 Å, p1 = p2 = 0.0, the transition state occurs. The internuclear distance vs time graph gives a relatively straight line which indicates a constant distance.

=== Comment on how the mep and the trajectory you just calculated differ. ===
The mep trajectory keeps the potential energy at the minimum in a straight line, whereas the dynamic trajectory is wavy.

r1 = 0.907, r2 = 0.917

Molecules and atome moving away from each other.

Setup a calculation where the initial positions correspond to the final positions of the trajectory you calculated above, the same final momenta values but with their signs reversed.

r1 = rts+δ, r2 = rts

final values of the positions r1(t) = 3.45, r2(t) = 0.72 and the average momenta p1(t) = -1.45, p2(t) = -2.48 at large t.

The molecule and the atom moving close together instead of moving apart.

=== Complete the table above by adding the total energy, whether the trajectory is reactive or unreactive, and provide a plot of the trajectory and a small description for what happens along the trajectory. What can you conclude from the table? ===

{| class="wikitable" border="5"
! P1!!P2 !! Etot!! Reactive?!!Description of the dyanmics!!Illustration of the trajectory
|-
| -1.25 || -2.5|| -99.08|| yes||The trajectory goes through the transition state and also go into the products. ||[[File:Surface01_ql2817.png]]
|-
| -1.5|| -2.0|| -100.22|| no||The trajectory falls back down into the reactants because there was not enough energy for reactants to pass over the transition state. || [[File:Surface02_ql2817.png]]
|-
| -1.5|| -2.5|| -98.91|| yes||The trajectory goes through the transition state and also go into the products with enough energy. || [[File:Surface03_ql2817.png]]
|-
| -2.5|| -5.0|| -84.62|| no||The trajectory was carrying enough energy towards products but then it shifts back into the reactants. || [[File:Surface04_ql2817.png]]
|-
| -2.5|| -5.2|| -83.40|| yes||The trajectory goes through the transition state and also go into the products with enough energy. || [[File:Surface05_ql2817.png]]
|}

=== State what are the main assumptions of Transition State Theory. Given the results you have obtained, how will Transition State Theory predictions for reaction rate values compare with experimental values? ===
Assumptions <ref name="main">https://en.wikibooks.org/wiki/Statistical_Thermodynamics_and_Rate_Theories/Eyring_Transition_State_Theory#Assumptions_of_Transition_State_Theory
</ref>

*Reactants are in constant equilibrium with the transition state structure.
*The energy of the particles follow a Boltzmann distribution.
*Once reactants become the transition state, the transition state structure does not collapse back to the reactants.

Transition state theory will predict a higher reaction rate than experimental one.

== '''Exercise 2: F-H-H system''' ==

===By inspecting the potential energy surfaces, classify the F + H2 and H + HF reactions according to their energetics (endothermic or exothermic). How does this relate to the bond strength of the chemical species involved? ===
F+H2:
r(AB)=1.5,r(BC)=0.74, AB,BC m=0
[[File:ql2817-01.png]]
exothermic, because the trajectory goes from a higher PE to a lower PE.
H+F2:
r(AB)=1.5,r(BC)=0.74, AB,BC m=0
[[File:ql2817-02.png]]
endothermic, because the trajectory goes from a lower PE to a higher PE.

===Locate the approximate position of the transition state. ===

===Report the activation energy for both reactions. ===

=== In light of the fact that energy is conserved, discuss the mechanism of release of the reaction energy. Explain how this could be confirmed experimentally.===

===Discuss how the distribution of energy between different modes (translation and vibration) affect the efficiency of the reaction, and how this is influenced by the position of the transition state. ===

=='''References'''==
<references/>:

File:Ql2817-02.png

2019-05-16T13:49:52Z

Ql2817:

File:Ql2817-01.png

2019-05-16T13:49:27Z

Ql2817:

MRD:ql2817