Kinetics and Equilibrium

Factors That Affect Reaction Rate  Increasing the temperature  Increasing the concentration  Increasing the surface area  Adding a catalyst  The reactants

Collision Theory  Concentration – Increasing the concentration of the reactant will cause more collisions between the particles  Surface Area – Collisions occur at the surface so increasing the surface means there will be more particles to collide.  Nature Of Reactants – Reactions depend on the reactants, usually reactions that involve ionic compounds react faster.  Temperature – When the temperature is raised it particles get excited. This causes them to move faster and collide more often.

Activation Energy

The activation energy of a reaction is the minimum collision energy. It depends on the kinetic energy of the colliding particles. If the points of collision are plotted on a graph, it will form a curve. Elementary Reactions

A reaction mechanism is a series of steps that make up an overall reaction. Each step is called an elementary reaction that causes the formation of molecules of ions. Molecules that are formed in a Elementary reaction than consumed in an later elementary reaction is called a reaction intermediate, because even though they aren’t a products or a reactants they are an important part of the for the reaction to happen.

Rate-Determining Step

Since elementary steps happen at different rates, the slowest one is called the rate-determining step.

Dynamic Equilibrium

Dynamic equilibrium occurs when the rate of the forward reaction is equal to the rate of the reverse reaction.

Equilibrium Constant If aA + bB  cC + dD then the value of the equilibrium constant is

c d Kc = [C] [D] [A]a[B]b

Don’t include liquids and solids in the equation

The best way to calculate the equilibrium constants is through the use of an I.C.E box

Fe + SCN  Fe(SCN)

Concentration (mol/L) Fe SCN Fe(SCN) Initial 0.0064 0.0010 0 Change -4.5x10-4 -4.5x10-4 4.5x10-4 Equilibrium 0.0064 5.5x10-4 4.5x10-4

Sometimes with the I.C.E box you will need to use the quadratic formula to solve for the equilibrium concentration. y=ax2+bx+c dsfadf x=- b±√b 2-4ac 2a Le Chatelier's Principle

Le Chateliers’ principle states that when a system in chemical equilibrium is affected by a change of temperature, pressure, or a concentration, the system shifts toward either the products or reactants.

 Adding more products shifts left  Adding more reactants shifts right  Adding pressure shifts towards the side with the least number of gas molecules  If heat is realised then shift left  If heat is added then shift right