6.1 Collision theory and rates of reaction

Sufficient energy, correct orientation / molecular geometry

What two factors are needed for a successful chemical reaction?

Change in mass, volume, and colour

What three things indicate that a chemical reaction has taken place?

The minimum amount of energy required by colliding molecules to react successfully

Define activation energy (Ea)

They provide a different pathway for the reaction with a lower Ea

How do catalysts speed up rate of reaction?

Temperature, pressure, surface areas concentration (of reactants / catalysts), presence of catalysts

What five factors affect rate of reaction?

Particles must collide with a kinetic energy greater than the activation energy, and have correct orientation / collision geometry for a successful chemical reaction to take place

Describe the collision theory

Absorb

Do endothermic reactions absorb or release energy?

Positive

Do endothermic reactions have positive or negative enthalpy change?

Products

Do the reactants or products have more energy in endothermic reactions?

Between the reactants' energy level and top of the curve

Where is activation energy on a potential energy diagram?

Between the reactants energy and product energy levels

Where is enthalpy change on a potential energy diagram?

Release

Do endothermic reactions absorb or release energy?

Negative

Do exothermique reactions have positive or negative enthalpy change?

X axis is potential energy, y axis is time (s)

Name the x and y axis of a potential energy diagram

By calculating the gradient of the line's linear section (rise / run)

How is rate of reaction calculated on a graph?

Temperature, concentration, surface area, pressure, catalysts

Which 5 factors effect rate of reaction?

- higher KE in particles

- increase in collision frequency

- more particles can overcome Ea barrier to react successfully

How does an increase in temperature affect rate of reaction?

- more reactant particles in the same volume

- increased collision frequency

- more successful collisions

How does an increase in concentration affect rate of reaction?

- decreased particle size

- more frequent contact

- more frequent successful collisions

How does an increase in surface area affect rate of reaction?

- particles closer together

- increased frequency of successful collisions

How does an increase in pressure affect rate of reaction?

- provide alternate rout for chemical reaction with lower Ea

- without raising temp. particles have sufficient KE to overcome Ea barrier

- more frequent successful collisions in less time

How does an increase in catalysts affect rate of reaction?

Water baths

How is temperature controlled?

Thermometer

How is temperature measured?

Titration (less reliable) or conductivity (more reliable - the more ions present the more conductive)

How is concentration measured?

A light spectrometer or colorimeter

How is colour change (light transmission) measured?

Balance

How is change in mass measured?

Gas syringe

How is change in volume of a gas measured?

Change in quantity / change in time

What is the formula for rate of change?

Energy distribution, probability of successful collisions, how factors affect number of particles with sufficient KE

What do Maxwell Boltzmann curves show?

Kinetic energy, proportional, temperature (Kelvin)

Average ... ... is ... to ... (in ...)

Know how to draw MB curve with affect of a catalyst

Know how to draw MB curve with varying temps