Rates of reaction

What is needed for a collision to be successful

Correct orientation and particles must have activation energy

Activation energy definition

The minimum energy required for a reaction to take place

How does rate of reaction change during a reaction

Starts at its quickest, and the rate gradually slows down

What factors can alter rate of reaction

Concentration/pressure

Temperate

Catalyst

Surface area

How does conc/pressure effect ror

Particles are closer together so particle collisions are more frequent collisions so more effective collisions

How to measure ror experimentally (2 ways)

Measuring the decrease in mass using a balance during a reaction or measuring the volume of gas produced

Catalyst definition

When a substance isn’t used up in a reaction and decreases the activation energy

Homogeneous catalyst

Catalyst thats in the same physical state as the reactants

Heterogeneous catalyst

Catalyst thats a different physical state as the reactants (usually solids with gaseous reactants)

How do catalysts work

Reactants are adsorbed onto the surface of the catalyst, where the reaction happens, then the products are desorbed

Benefits of using a catalyst

Lower cost than increasing temp/pressure

Reduces energy needed without being used up

Less CO2 produced as less energy needed

What does the boltzmann distribution look like

How does boltzmann distribution change with temperature

T2 = higher temp

What does the area under the boltzmann distribution represent

The number of molecules

How does a catalyst affect the boltzmann distribution

What makes a system in dynamic equilibrium

When the products are being made at the same rate as reactants are being made in a closed system and the concentrations do not change

What is le Chatelier’s principle

The equilibrium will move to minimise an external change

How does changing concentration affect equilibrium

An increase to one of the sides will shift the equilibrium to the opposite side, and a decrease to one of the sides will shift the equilibrium to that side

How does changing temperature affect equilibrium

Decreasing temperature will shift the equilibrium in the exothermic direction, increasing temperature will shift the equilibrium in the endothermic direction

How does changing pressure affect equilibrium

If pressure is increased, the equilibrium will shift to the direction with less gaseous moles and if pressure is decreased, the equilibrium will shift to the direction with more gaseous moles

Equation for Kc

What does the value of Kc tell us about the equilibrium

Greater than 1: Shifted to the right (products)

1: in the middle

Less than 1: shifted to the left (reactants)

Benefits of a homogeneous catalyst

Increases reaction rate more than hetero because its mixed in with the reactants

Benefits of a heterogeneous catalyst

Easier to remove the catalyst from the reaction mixture

How does surface area affect the rate of reaction

Increasing the surface area will increase the number of molecules that can collide which will increase the frequency of collisions, hence frequency of successful collisions