CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Kinetics
Catalysts and the activation energy barrier
- 3 things to know
- Unit AS 2
Overview
What a catalyst does to a chemical reaction, how a catalyst changes the reaction profile of a reaction and catalyst used in the Haber process.
What you need to know
Answer each one before you reveal it.
How is the effect of a catalyst shown on a Maxwell–Boltzmann diagram?
Why does moving the activation energy line to the left increase the rate so markedly?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State what a catalyst does to a chemical reaction.
Model answer
A catalyst increases the rate of the reaction and is recovered chemically unchanged at the end of it.
- 2
By what means does a catalyst increase the rate of a reaction?
Model answer
It provides an alternative reaction pathway that has a lower activation energy than the uncatalysed route.
- 3
How is the effect of a catalyst shown on a Maxwell–Boltzmann diagram?
Model answer
A second vertical line is drawn further to the left, at the lower activation energy of the catalysed route.
- 4
Does adding a catalyst change the shape of the Maxwell–Boltzmann curve?
Model answer
No, the shape of the curve depends only on the temperature, which the catalyst does not alter.
- 5
Why does moving the activation energy line to the left increase the rate so markedly?
Model answer
A far greater area of the curve then lies to the right of the line, so many more molecules have enough energy to react on collision.
- 6
Describe how a catalyst changes the reaction profile of a reaction.
Model answer
The hump between the reactant and product levels is lowered, while the positions of the two levels themselves are unchanged.
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