Chapt 12 - Chemical Kinetics

7/30/2019 Chapt 12 - Chemical Kinetics

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Chapter 12: Chemical Kinetics


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Introduction

The study of conditions affecting reactions andrate at which they are occurring is called

CHEMICAL KINETICS.


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Rate of Reaction

The RATE of a reaction =SPEED at which a reactionhappens.

The RATE at which the reactants are transformed

into the products of the reaction.

e.g. A B + C


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Rate of Reaction

The term RATE describes the change in a quantitythat occurs per unit of time.

t

)(Rate of Reaction =

The symbol means change in and the bracket

indicates concentration.


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Instantaneous Rates of Reaction

Refers to Rate or Speed of the reaction at onemoment in time.

changes throughout the reaction because

the concentrations change non-linearly over time.


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We calculate the average rate over a given intervalof time.

Instantaneous Rate of Reaction =dt

d )(


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The rate of reaction at every point on graph isdirectly propertional to the concentration of the

reactants at that moment in time.

Rate = k (concentration of reactants)n

Describes the rate of reaction, known

as the RATE LAW for the reaction.


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The rate of reaction is proportional to theconcentration of reactants.


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Order of Reaction =MOLECULARITY

It gives you information about which concentrationsaffect the rate of the reaction.

To find out the ORDER of reaction, we need to write

down each step in the reaction.

Each step have its own order.

The order of reaction simply counts the number of

species (molecules, ions, atoms or free radicals) takingpart in that step.


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Chemical Equilibrium

Most chemical reactions were not reversible they could notgo back to the reactants once the products are formed.

But it is normal in a chemical reaction that not all the

reactants become products.

Some chemical reactions however will go backwards and

forwards depending on The conditions known as REVERSIBLE

REACTION.


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Chemical Equilibrium

In other words, both forward and backwardreaction will occur.

When the forward reaction is happening at the

SAME rate as the backward reaction, thereactions are in Equilibrium.


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Factors affecting Equilibrium

When a bunch of molecules are left alone, they

reach a state of equilibrium. But that position ofequilibrium can change if something happens tothe molecules. Here's a list of things which canchange the equilibrium point...

(1) Catalysts are added.(2) The temperature of the system ischanged.(3) The pressure of the system is

changed.(4) The concentrations are changed,like adding more water to a solutionor adding more of one substance.

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Chapt 12 - Chemical Kinetics