Kinetics Lesson 4 PE Diagrams

Potential Energy Diagrams Exothermic Show the change in potential energy or enthalpy during a successful collision. Standard Notation:   H2 + I2 → 2HI + 170 kJ ΔH Notation: H2 + I2 → 2HI ΔH = -170 kJ Both notations indicate an exothermic reaction. The first indicates that 170 KJ of KE are produced, while the second shows that the PE decreases by 170 KJ. On the right Or negative

Two reactants collide and form a complex species Activated Complex Two reactants collide and form a complex species

ΔH Forward/Enthalpy change Exothermic Reaction ΔH= -

ΔH Reverse/Enthalpy change Endothermic Reaction ΔH=+

Potential Energy Diagrams   Kinetic Energy (kJ) Heat energy due to the motion of particles. Simulation Potential Energy . ΔH means change in enthalpy It is also called the heat of the reaction because it tells you how much heat or KE was produced or consumed by the reaction. Bond Energy (kJ)

PE + KE = Total Energy is constant   Conservation of Energy PE KE ΔH Reaction Type Decreases Increases -ve exothermic Increases Decreases +ve endothermic When PE (bond energy) decreases it is converted into KE which increases. Remember that KE is heat energy, so it gets hotter and it is exothermic.

Ea (energy of activation) Always +ve, given from outside

Required for forward reaction Ea (Forward) Required for forward reaction

Required for reverse reaction Ea (Reverse) Required for reverse reaction

Which reaction is fast? Forward or reverse?

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 KJ 1. An H2 and I2 approach each other

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 1. Reactants H2 and I2 approach each other Reactants PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 2. They collide and become an Activated Complex PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 2. They collide and become an Activated Complex Unstable Reaction Intermediate High PE Low KE Bonds Break & Form Reactant bonds break Activated complex bonds form PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 3. New bonds form and products separate PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 3. New bonds form and products separate activated complex bonds break product bonds form PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 3. New bonds form and products separate Activated Complex Reactants Products PE Reaction Path

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 3. New bonds form and products separate PE Reaction Path Ea(for) Ea(rev)

Lets Explore the Potential Energy Changes during a Single Collision H2 + I2 → 2HI + 170 kJ 3. New bonds form and products separate PE Reaction Path Ea Ea(rev) ΔH = -ve

Relationship ship between Ea(f), Ea(r) and ΔH

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the activation energy is 200 kJ H2 + I2 → 2HI ΔH = -170 kJ     600 400 200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the activation energy is 200 kJ H2 + I2 → 2HI ΔH = -170 kJ     600   reactants 400 200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the activation energy is 200 kJ H2 + I2 → 2HI ΔH = -170 kJ     600   reactants Ea 400 200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the activation energy is 200 kJ H2 + I2 → 2HI ΔH = -170 kJ     600   reactants Ea 400 ΔH 200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the activation energy is 200 kJ. H2 + I2 → 2HI ΔH = -170 kJ       600   reactants Ea 400 ΔH 200   PE (KJ) Reaction Path

Workbook Page 25 Question 41-45

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path  

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path  

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path  

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path  

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path   ΔH = + 100 KJ

Draw the PE diagram if the enthalpy of the reactants is 400 kJ and the energy of the activated complex is 600 kJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path   ΔH = + 100 KJ

Draw the PE diagram if the enthalpy of the reactants is 400 KJ and the energy of the activated complex is 600 KJ.   I2 + Cl2 + 100 KJ → 2ICl    PE 600 400 200 Reaction Path   Ea ΔH = + 100 KJ

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   400   200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   400   200   PE (KJ) Reaction Path

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   400   200   PE (KJ) Reaction Path Ea (rev) = 400 kJ

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   400   200   PE (KJ) Reaction Path Ea (rev) = 400 kJ

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   Ea (for) = 200 kJ   400   200   PE (KJ) Reaction Path Ea (rev) = 400 kJ

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   Ea (for) = 200 kJ   400   200   PE (KJ) Reaction Path Ea (rev) = 400 kJ

Draw the PE diagram if the enthalpy of the products is 200 kJ, the Ea (for) = 200 kJ, and Ea (rev) = 400 kJ     600   Ea (for) = 200 kJ   400   200   PE (KJ) Reaction Path Ea (rev) = 400 kJ ΔH = -200 kJ

Exothermic or Endothermic? Exercise Exothermic or Endothermic?

Exothermic or Endothermic? Exercise Forward reaction is Exothermic or Endothermic?

Exothermic or Endothermic? Exercise Reverse reaction is Exothermic or Endothermic?

What is Ea for forward reaction? Exercise What is Ea for forward reaction?

What is Ea for reverse reaction? Exercise What is Ea for reverse reaction?

Exercise Which species has strongest bond? Clue: stronger the bond, higher the energy need to break the bond.

Exercise Which species has weakest bond? Clue: stronger the bond, higher the energy need to break the bond.

What is ΔH for reverse reaction? Exercise What is ΔH for reverse reaction?

What is ΔH for forward reaction? Exercise What is ΔH for forward reaction?

What is activated complex? Exercise What is activated complex?

Which set of species has highest PE? Exercise Which set of species has highest PE?

Which set of species has highest KE? Exercise Which set of species has highest KE?

Which set of species has lowest KE? Exercise Which set of species has lowest KE?

Which set of species is fastest moving particles? Exercise Which set of species is fastest moving particles?

Which set of species is slowest moving particles? Exercise Which set of species is slowest moving particles?

Which reaction should be faster? Exercise Which reaction should be faster? Forward or Reverse

Summary Activated complex Breaking bond require energy and making bond give off energy KE and PE conversion at collision Speed of molecules based on KE Stability of species based on PE ΔH Forward/Enthalpy change Ea (energy of activation) forward and reverse Slow and fast reaction based on Ea Strength of Bond based on Ea of reaction Ea(f) Ea® ΔH relationship and calculation

Worksheet 1.2

KE Distribution Curve

Write two facts about this graph? Distribution Curve   Write two facts about this graph?

Distribution Curve  

Draw a Distribution Curve for student marks 47 8 74 15 49 41 51 52 62 22 59 28 55 73 84 1 31 38 87 16 63 11 56 25 57 32 60 36 42   Write two facts about the distribution of marks

Draw a Distribution Curve for student marks   Write two facts about the distribution of marks Is it a group of strong student or weak? How will graph be different if it is not a group of strong students?

Kinetic Energy Distribution Curve  

Kinetic Energy Distribution Curve   Are all molecules in this room moving? Do they have KE? Do all molecules have same amount o f KE? Predict a distribution curve of KE of molecules? How will KE distribution curve of a warm water flask be different from an ice cube?

Kinetic Energy Distribution Curve  

PE(kJ) reaction path Slow rate due to high Ea

PE(kJ) 500 400 300 200 100 reaction path Increasing the temperature does not change the diagram. It gives more collisions the required Ea and more are successful. Increasing the concentration, pressure, and surface area does not change the diagram.

Page 19 Question 29-30

Summary Activated complex Breaking bond require energy and making bond give off energy KE and PE conversion at collision Speed of molecules based on KE Stability of species based on PE ΔH Forward/Enthalpy change Ea (energy of activation) forward and reverse Slow and fast reaction based on Ea Strength of Bond based on Ea of reaction Ea(f) Ea® ΔH relationship and calculation KE distribution curve