1. Collision Theory and Reaction Rate

2. a) Collision Theory: THE HOME RUN ANALOGY: In order to hit a home run out of the park) one must: ________________________ _____________________________________________ In order for a chemical reaction to occur, the reacting particles (atoms, ions, or molecules) must _________. They must collide with sufficient _______ AND they must collide with the proper ____________ in space. THIS IS CALLED THE _____________ THEORY! The rate (or speed) of a reaction is determined by the number of ___________ collisions occurring in a unit amount of time. collide energy orientation 3) hit the ball at just the right angle. 1) hit the ball, COLLISION effective 2) hit the ball hard enough and

3. Collision Theory and Reaction Rate N 2 + O 2 N 2 O 2 Activated complex NO + NO

4. Collision Theory and Reaction Rate N 2 + O 2 → NO + NO REACTANTSPRODUCTS

5. Collision Theory and Reaction Rate b) Factors that Affect the Rate of Reaction: 1)Nature of the Reactants: _________________________________________ _________________________________________ Gaseous reactants or aqueous ionic reactants generally react quickly. Reactants that are in different phases tend to react more slowly. homogeneous reactions are reactions in which all the reactants are in the same phase. all the reactants are in different phases. heterogeneous reactions are reactions in which

6. Collision Theory and Reaction Rate 2)Reaction Mechanism: _________________________________________ 3)Concentration: _________________________________________ 4) Pressure: _________________________________________ rate determining step. Reactions with simple mechanism are usually faster than reactions with complex mechanisms. The slowest step in the mechanism is called the will usually increase the rate of reaction. Increasing the concentration of the reactants Increasing the pressure on GASEOUS reactants will usually increase the rate of reaction.

7. Collision Theory and Reaction Rate 5)Temperature: _________________________________________ 6)Surface Area: _________________________________________ 7) Catalyst: _________________________________________ Increasing the temperature of the reacting system will usually increase the rate of reaction. Increasing the surface area of the reactants will usually increase the rate of reaction. The addition of a catalyst will usually increase the rate of reaction.

8. Collision Theory and Reaction Rate Ex.1) Adding a catalyst will lower the activation energy of the forward reaction (1) more than the reverse reaction (2) less than the reverse reaction (3) the same as the reverse reaction Ex.2) How does lowering the minimum energy required for the rate determining step (the slowest step in the reaction mechanism) effect the overall reaction rate? (1) it increases the overall rate (2) it decreases the overall rate (3) it has no effect on the overall rate

9. Collision Theory and Reaction Rate Ex.3) A reaction between a solid substance and a gaseous substance is a(n) (1) endothermic reaction (2) solution reaction (3) homogeneous reaction (4) heterogeneous reaction Ex.4) A description of the experimentally verified steps in a reaction is an example of (1) the net reaction (2) Hess’ Law (3) the activated complex (4) the reaction mechanism

10. Collision Theory and Reaction Rate Ex.5) If the activation energy is very high for a reaction, the rate of reaction usually (1) unaffected by a temperature change (2) is slow (3) is independent of concentration (4) is fast Ex.6) Translational energy is the energy a molecule possesses from (1) the motion of its atoms toward and away from each other (2) the disintegration of its nuclei (3) its motion from place to place (4) its rotation on its axis

11. Collision Theory and Reaction Rate Ex.7) In order for a chemical reaction to occur (1) the reactants must be vaporized (2) chemical bonds must be destroyed (3) the temperature must be above 0 o C (4) collisions must occur between reactant particles Ex.8) The activation energy for the forward reaction... A + B  C + 35 kcal... is 25 kcal. The activation energy for the reversed reaction is (1) 10 kcal (2) 60 kcal (3) 25 kcal (4) 35 kcal 35 kcal 25 kcal ? kcal

12. Collision Theory and Reaction Rate Ex.9) In a reversible chemical reaction, the net change in heat involved in the endothermic reaction is (1) greater than that of the exothermic reaction. (2) smaller than that of the exothermic reaction. (3) equal to that of the exothermic reaction. Ex.10)As the temperature of a reacting system is raised, the rate of the chemical reaction (1) decreases (2) increases (3) remains the same

13. Collision Theory and Reaction Rate Ex.11)For reasons of stability, one fundamental drive of chemical reactions is toward (1) lower enthalpy (2) higher enthalpy (3) a continuous yield of product (4) a lower temperature Ex.12)If the pressure on a gaseous system is increased, the rate of reaction is increased because (1) the activation energy is increased (2) the concentration is increased (3) the temperature is increased (4) the reacting volume is increased