**Kinetics**

The study of the rate at which a chemical reaction occurs

You can't forget

**from AS. A2 builds upon this**__Kinetics__An increase in

An increase in

A

An increase in

**temperature**increases the**average kinetic energy**of the particles hence increasing the fraction of particles with the**activation energy**required for a**successful collision**. This increases the rate of reactionAn increase in

**concentration**and**pressure**increases the likelihood of a**successful collision**as particles are**closer**together. This increases the rate of reactionA

**catalyst****lowers the activation energy**thus more particles have the activation energy, increasing the chance of a**successful collision**. This increases the rate of reactionAn increase in

**surface area**increases the likelihood of a**successful collision**as there are**more**particles**available**to react. This increases the rate of reaction**Reaction Rates**

Chemical reactions don't occur instantaneously and so the concentration over the period of a reaction can be measured

Lets consider the reaction of

Lets consider the reaction of

**A → B**The steeper the curve the faster the rate

The initial slopes are steepest because at the beginning there is the greatest concentration of reactants

The initial slopes are steepest because at the beginning there is the greatest concentration of reactants

This means that

Change in time__Change in products or reactants__= RateChange in time

However, the two lines don't have a constant gradient which means a changing rate

This means that to take the rate only the gradient at one point can be taken using the tangent

This means that to take the rate only the gradient at one point can be taken using the tangent

In words the rate of reaction can be expressed as

**The increase/decrease in concentration of a product/reactant as a function of time****Rate Equation**

The rate equation's relation to the general equation is:

As you can see the

This means the rate equation must be found through

When the power is

When the power is

**coefficients don't appear**in the equationThis means the rate equation must be found through

**experimentation****'k'**stands for the**reaction constant**. It remains constant for that one reaction but it's**units change**When the power is

**one**the reaction is**first order**When the power is

**two**the reaction is**second order**etc.**Working out the reaction constant's unit**

This is an example frame

**Discovering the orders in a reaction**

Some of the reactants react quicker in a reaction which increases the rate of the equation

How much faster they do this by is called the order and on the reaction equation it is the power

How much faster they do this by is called the order and on the reaction equation it is the power

**Rate Determining Step**

**The rate determining step is the intermediate reaction which determines the rate of the whole reaction**In every process there is always a point in the process which determines how fast the end result is reached.

When making a cup of coffee the rate determining step is the length of time the water takes to boil as this takes the longest of all the processes involved in the making process.

In a chemical reaction you can't time the rate determining step.

Instead you use the

**intermediate reactions**and the

**rate equation**

Take the equation

**A + D → F + G**

**A + B → C (1)**

C + D → B + E (2)

E → F + G (3)

Rate = k[A][B]

C + D → B + E (2)

E → F + G (3)

Rate = k[A][B]

Using this information it shows that

**S**

**tep 1**is the

**rate determining step**as both chemicals in the rate equation appear in step 1.

This information also tells us that

**B is a catalyst**and

**C and E**are

**intermediates.**

**If Step 2 or 3**was the rate determining step then any chemicals from

**earlier reactions**can

**appear**in the

**rate equation**as they too contribute to the time of the reaction.