2.6.4Unit 2. Energetics, Group Chemistry, Halogenoalkanes and Alcohols
Catalysts and Energy — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions
5 min read 4 parts Lesson 40 of 53 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 4What a Catalyst Does
A catalyst speeds up a reaction but is not used up overall.
Alternative route
- Alternative route A catalyst gives the reaction another pathway with a lower activation energy.
Unchanged
- Unchanged It is chemically unchanged at the end, so only a small amount is needed.
No change to ΔH
- No change to ΔH It does not alter the enthalpy change, because reactants and products are the same.
Equilibrium
- Equilibrium It speeds up forward and reverse reactions equally, so it does not change the position of equilibrium.
Types
- Types Heterogeneous catalysts are in a different phase from the reactants, while homogeneous ones are in the same phase.
Selectivity
- Selectivity Some catalysts favour one product, so industry can obtain more of the desired product with less waste.
Section 2 of 4Reaction Profile and Distribution
1
On a reaction profile the uncatalysed route has a high peak, and the catalysed route has a lower peak.
2
On a Maxwell-Boltzmann curve a second line for the catalysed Eₐ is drawn to the left of the original one.
3
The area under the curve to the right of the lower Eₐ is larger.
4
A greater proportion of molecules now have enough energy to react.
5
The rate of the catalysed reaction is higher at the same temperature.
6
The total area under the curve is unchanged by a catalyst, because the number of molecules is the same.
Section 3 of 4Industrial Importance
Industrial Importance
Iron
- Iron Iron is used as the catalyst in the Haber process for making ammonia.
Vanadium(V) oxide
- Vanadium(V) oxide V₂O₅ is used as the catalyst in the Contact process for making sulfuric acid.
Catalytic converters
- Catalytic converters Platinum and rhodium convert harmful exhaust gases such as CO and NO into CO₂ and N₂.
Benefits
- Benefits Catalysts allow lower temperatures, which saves energy, cuts fossil fuel use and reduces emissions.
Poisoning
- Poisoning Impurities can bind to the surface of a heterogeneous catalyst and reduce its activity, so reactants are purified first.
Section 4 of 4Exam Checklist & Tips
2.6.4 – Key Points for the Exam
- Catalyst A substance that increases the rate of a reaction without being used up.
- Heterogeneous catalyst A catalyst in a different phase from the reactants.
- Homogeneous catalyst A catalyst in the same phase as the reactants.
- Reaction profile A diagram of energy against progress of reaction showing Eₐ and ΔH.
Common Mistakes
- Saying a catalyst increases the energy of the molecules rather than lowering Eₐ.
- Believing that a catalyst changes the position of equilibrium or the yield.
- Showing the catalysed profile with different reactants or products from the uncatalysed one.
- Saying a catalyst is used up; it is regenerated.
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