OZ 4: Ozone- here today gone tomorrow

Steady state

ozone is being made as fast as it is used up

Equation for rate of reaction

Rate of reaction= change in property / time taken

What are 5 changes in property?

1. Measuring volume of gases

2. Measuring mass change

3. pH measurement

4. Colorimetry

5. Chemical Analysis

What are two pieces of equipment that can measure the volume of gas produced?

1. Measuring cylinder

2. Gas syringe

What do you use to measure mass change?

electronic scale

What do you use to measure pH?

1. pH probe

2. universal indicator

A colorimeter measures

the change in colour of a reaction

A colorimeter detects

how much light is absorbed by the solution

A higher absorbance of a colorimeter means

more of the coloured species is present

A lower absorbance of a colorimeter means

the coloured species is being used up

How can you use chemical analysis?

1. take a sample of reaction mixture at regular intervals

2. stop reaction in sample

3. analysis

quench

stop reaction

Example of chemical analysis

titration

What are the 5 factors that affect rate of reaction?

1. Concentration

2. Temperature

3. Intensity of Radiation

4. Surface Area

5. Catalyst

collision theory

The idea that reactions occur when particles collide with enough kinetic energy.

Activation enthalpy

minimum kinetic energy required by a pair of colliding particles before a reaction will occur

Reactions occur when particles

collide with activation energy

Why don’t all collisions lead to a reaction?

Particles must collide with enough energy to overcome the activation energy barrier

What does the peak of an enthalpy profile represent?

transition state

transition state

point where old bonds stretch and new bonds start to form

How do catalysts affect a reaction?

They provide an alternative pathway with lower activation energy, increasing the rate.

The distribution of kinetic energy at a given temperature is given by the

Maxwell- Boltzmann distribution

At a higher temperature, more particles

have minimum energy to react

If temperature is raised, M-B graph

shifts to the right and the peak is lower

Reactions go faster at higher temperatures since

a larger proportion of colliding molecules have minimum activation enthalpy needed to react

peak of a M-B diagram represents

most probable energy

area under M-B curve

all particles

activation energy in M-B curve is on the

right

What effect does adding a catalyst have to a M-B curve?

curve remains the same

E_a shifts to the left so more particles can react

How does concentration affect the rate of reaction?

Higher concentration increases the frequency of collisions.

Why does increasing temperature speed up a reaction?

Particles move faster and collide more often with greater energy.

How does radiation intensity affect reaction rate?

More radiation provides energy to break bonds faster.

Why do smaller particles react faster than larger ones?

They have a larger surface area, leading to more collisions.

How do catalysts increase the rate of reaction?

They lower the activation energy, allowing more collisions to be successful.