Kinetics: study of rate or speed at which Reactions occur. Unit 8 :Chapter 16 and 17 Kinetics: study of rate or speed at which Reactions occur. a reaction is the BREAKING and REFORMING of bonds to make enitirely new compounds as products. Reaction Mechanism= Step by Step needed to make a product (like a recipe) Just like you bake a cake we must follow directions CAN’T OMIT ANY STEPS CAN’T CHANGE ORDER OF STEPS CAN’T OMIT any REACTANTS (ingredients)

What Determines the Rate of Reaction? # of steps: more steps slower the reaction Rate Determining Step: the slowest step of the reaction; most importat factor influencing reaction rate. Collision Theory: Reactions only take place if there are effective collisions. They need: 1. Proper amount of energy 2. Proper orientation/alignment *****NEED EFFECTIVE COLLISIONS for reactions to take place. Activation Energy(Eact) minimum amount of energy needed to start a reaction.

Activated Complex: (AC) immediate substance form waiting to see if effective collisions take place. Unstable Ex Reactants AC

Factor How Rate Affected Why does it increase the rate? Nature of Reactants IONIC:substances react Faster Covalent: substances react slower IONIC: Smaller less bonds to break Covalent: larger more bonds to break (more steps)

2. Concentration Increase Concentration= Increase rate 3. Pressure INCREASE press = Increase Rate GASES ONLY!!! 4. Temperature Increase Temp = Increase rate

5. Surface Area Increase SA (make pieces smaller)= Increase rate 6. Catalyst

PE of the Products-PE of the Reactants Heat of Reaction =the amount of heat ENERGY LOST or GAINED throughout a Reaction enthalpy PE of the Products-PE of the Reactants Also recall, there are 2 types of reactions: 1. Reactions that release energy exothermic is negative (-) A + B  C + ENERGY Ex Sodium in water  heat (fire) as product 2. Reactions that absorb/ gain energy  endothermic iis positive (+) A + B + ENERGY  C Ex baking (need oven to supply heat)

How do I interpret Table I: Look at the equation on your paper: 1. If it’s written the same keep the sign you see on Table I 2. If it’s written in reverse you must reverse the sign you see on Table I whatever you do to a chemical reaction you also must do to the Ex 1 If you REVERSE a reaction (flip the products and reactants) then you must Reverse the sign for Ex2 If you double the equation (or coefficients) then you must double the

Ex#1 H2O(l)  H+(aq) + OH-(aq) Is it written the same? Do you reverse the sign? H=?

III. Potential Energy Diagram1 1=PE Reactants 4= EACT REV RXN 2=EACT FWD RXN 5= 3= Activated Complex (AC) 6= PEProducts

Stays the same Changes with catalyst added PE Reactants 1. EACT FWD RXN PEproducts 2. EACT REV RXN 3. 3. AC

Equilibrium: when the rate of the FWD RXN=rate REV RXN in a closed system

Types of Equilibrium Phase Equilibrium: occurs during a phase change Ex 2.

3. Haber: Process used by Germans during WW1 to pull nitrogen out of the air to make ammonia

Lechatelier’s Principle: When a stress is applied to a system, the reaction will try to shift in a direction that will relieve that stress Right=shifts means that the fwd rxn is predominate until eq. is reestablished. Arrow=  more product is made Left= shift means that the reverse reaction is predominate until eq. is reestablished. Arrow= more reactant is made

[ ]: Concentration [ ] Increase [ ]=shifts to other direction to make less Decrease [ ]= stays on that side to make more Ex. N2(g) + 3H2(g) > 2NH3(g) Increase [N2] shifts? Decrease [H2] shifts? Increase [NH3] shifts?

Increase pressure shifts? Decrease pressure shifts? Effect Pressure Gases ONLY!!!!!!!!!! Increase pressure=shifts to side with lesser # of moles Decrease pressure = shifts to side with greater # of moles Ex: N2(g) + 3H2(g) > 2NH3(g) Increase pressure shifts? Decrease pressure shifts?

H2(g) + I2(g) <-> 2HI (g) Increase pressure shifts? Decrease pressure shifts?

4Al(s) + 3O2(g) <-> 2Al2O3 (s) Increase pressure shifts? Decrease pressure shifts?

Effect of temperature=same as [ ] Increase temperature= shift to other side Decrease temperature = stay on that side Ex 2H2(g) + O2(g) <-> 2H2O(g) + 483.6kJ Increase Temperature shifts? Decrease temperature shifts? 2H2O(g) + 483.6kJ <-> 2H2(g) + O2(g) Increase temp shifts? Decrease temp shifts?

Balance the equation and apply the stresses. N2(g) + H2(g_  NH3(g) + 91.8kJ N2(g) increased____ 7. Pressure Increased___ NH3(g) increased ___ 8. Pressure Decreased___ H2(g_ increased___ 9. Temp Increased___ N2(g) decreased____ 10. Temp Decreased___ NH3(g) decreased ___ H2(g_ decreased___

2HgO(s) + 10kcal 2Hg(l) + O2(g) Increase Pressure= Increase temp= [HgO] increased= [Hg] Increased= Temp Decreased= Presure decreased= [O2]decreased= Catalyst= [HgO] decreased=

2CO(g) + O2(g)  2CO2(g) + 566kJ Press increased= 8. catalyst= Temp increased= 9. [CO] decreased- [CO] increased= [CO2] increased= Temp decreased= Pressure decreased= [O2] decreased=