Kinetics Studies the speed of chemical reactions

Reaction Rate can be measured in: time (sec, min, hr) mass/time (lb/sec, kg/hr) moles/time.

BATCH

For a Batch Process the Reaction Rate is calculated by time (sec, min) to complete the reaction

CONTINUOUS

Reaction Rate for Continuous Process moles/hr, kg/hr, kg/s, etc. –How much product is being formed per time (manufacturing) –How quickly a reactant is being used per time (pollution control) kJ/hr, J/s, etc. –How much energy is being released/absorbed per time (energy production)

How is the Rate of a Chemical Rxn Changed?

Kinetic Theory The kinetic theory of gases & fluids describes a gas as many small particles (atoms or molecules) which are in constant, random motion. The rapidly moving particles constantly collide w/ each other & w/ the walls of the container.

Collision theory states that reactions occur when reactants hit in the proper orientation with enough force to cause a reaction.

Petri Dish Demonstration or Video of Kinetic and Collision Theory

If you can increase the number of collisions or force of the collisions you will change reaction rates.

Factors that effect the rate because they effect on number of collisions

Concentration Concentration is defined as the amount of material (mass, mol) per volume. Increasing concentration increases chances of collision because more reactants in same volume.

Oxidation of Fe Wool Demo

Surface Area of the Reactants The more exposed the reactants are to each other the greater the chance of a collision. BETTER

In what state of matter does a reaction proceed most quickly? Gases are the best BETTER

Water Cooler Gone Wrong

Mixing If you mix a reaction solution you increase the chances of reactants coming in contact by increasing motion of reactants and exposing reactants.

Heat increases speed of atoms and molecules making it more likely they will come in contact.

Factors that effect the force of collision (or the force necessary)

Heat also increases the force of collisions

Catalysts lower the amount of force / energy needed.

Catalysts help convert reactants into products by making a different activated complex

Catalysts change the reaction by changing the pathway

Sometimes a single step rxn is broken down into several steps making rxn easier

List of Factors that Can Effect the Reaction Rate Concentration Energy - Heat, Light Catalysts Surface Area (inc. State of Matter) Mixing

END

Heat and Energy –There is always a need for activation energy. This energy is used to break bonds and overcome repulsion forces of valence electrons. Activation Energy

Determining Rate Laws Page 574 sample problem, 575 sample problem, 582 #12 and 16

Rate Law A + B  C R c = k[A] x [B] y

Energy Absorbed or Released by a Reaction and the Speed of the Reaction are Different. Fast and Lots of Energy are Explosions

Notice that just like the instantaneous speed for a car is not the same as its average speed, the instantaneous rxn rate of a chemical rxn is not equal to its average rxn rate

INSTANTANEOUS Reaction aA + bB  cC + dD [A] a [B] b rate = Constant for specific reaction at a specific temperature, reaction vessel, etc. k k

Solids are not involved in reaction rates because their concentration does not change. Their surface area though would be present in the constant.

Notice that the length of reaction and reaction rate are inversely proportional. As one goes up the other goes down.

Many reactions consist of several steps one of which will be RATE LIMITING and so this step will determine the speed for the entire rxn

2O 3 + hv  3O 2 Important reaction

Dueling Ozone Rxns in the Atmosphere O 2 (g) + hv  2 O (g) 2 O (g) + O 2 (g)  O 3 (g) CFCl 3 (g)  CFCl 2 (g) + Cl Cl (g) + O 3 (g)  ClO + O 2 (g) BOTTOM RXN IS VERY SLOW

We will move on to solutions, molarity and equilbrium next

Dissolving Knowing what factors influence the rate of a chemical reaction, what factors would influence the rate at which a solute would dissolve into the solvent?

2 SO 2 (g) + 2 NO 2 (g)  2 SO 3 (g) + 2 NO (g) 2 NO (g) + O 2 (g)  2 NO 2 (g) 2 SO 2 (g) + 2 O 2 (g)  2 SO 3 (g) The lead chamber process which used to be a major step in a process to make Sulfuric Acid uses nitrogen dioxide as a catalyst