Module 3

Lesson 11 – Catalysis

Objectives

MustState that a catalyst speed up the reaction but are not consumed during it.ShouldDescribe how catalysts often requiring lower temperatures and reducing energy demand and CO2 emissions. CouldExplain the effect of the proportion of molecules possessing greater than or equal to activation energy on rate of reaction.

Starter - Definitions

Catalysts are substances which increase the rate of a chemical reaction without being consumed by it themselves.

They do this by providing an alternative route for the reaction with a lower activation energy.

Benefits of catalysts

Describe and explain three potential benefits of using catalysts in an industrial process.

Did you get?

• Lower temperatures and pressures required therefore reducing energy demand.

• Different reactions can be used with better atom economy thus reducing waste

• Lower production costs• Catalysts can be used to generate specific

products

Maxwell-Boltzmannactivation energy(catalysed)

activation energy(uncatalysed)

EaEacat

The effect of temperature

• We would expect rate to increase with increasing temperature because the number of collisions increases.

• However, we also know that particles need a minimum amount of energy to react when they collide. We call this the ACTIVATION ENERGY.

• If particles do not have enough energy when they collide they simply bounce off each other.

• Increasing temperature gives the particles more energy and so more of them have enough energy to react when they collide.

Enthalpy profiles

products

Ea

Ec

ΔH

Past paper question

Mark scheme

Mark scheme

Past Paper Question

7 marks

Practical Demonstration

• Decomposition of H2O2 with and without a catalyst (MnO2)

Catalase in liver

• Catalysts are often enzymes, generating very specific products and operating effectively close to room temperatures and pressures.

• Demonstration or video http://www.youtube.com/watch?v=hR38o2Ec8b0

• Denaturing

Plenary – industrial processes

Catalysts have a wide range of crucial industrial applications. Ones you should be aware of include:• Iron in ammonia production• Ziegler Natta catalyst in poly(ethene)

production• Platinum, palladium and rhodium in catalytic

converters

Examination question

Mark scheme