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Chemical energetics

Chemical energetics

Exploring the Energetic World of Chemical Reactions and Thermodynamics

Introduction to Chemical Energetics:

Definition and scope of chemical energetics in the context of A Level Chemistry.
Importance of understanding energy changes in chemical reactions.
Thermodynamics and Energy:

Fundamental principles of thermodynamics and their application to chemical systems.
Overview of energy transfer, work, and heat in chemical reactions.
Enthalpy and Enthalpy Changes:

Definition and significance of enthalpy in chemical reactions.
Calculation and interpretation of enthalpy changes (∆H) using Hess's Law and bond enthalpies.
Spontaneity and Gibbs Free Energy:

Understanding spontaneity and the concept of Gibbs free energy (∆G) in determining reaction feasibility.
Relationship between enthalpy, entropy, and temperature in predicting reaction spontaneity.
Bond Energies and Thermochemical Equations:

Exploring bond energies and their role in quantifying energy changes in chemical reactions.
Use of thermochemical equations to calculate enthalpy changes.
Standard Enthalpy Changes and Standard Conditions:

Definition and determination of standard enthalpy changes (∆H°) under standard conditions.
Application of standard enthalpy changes in calculating reaction enthalpy.
Calorimetry and Heat Measurements:

Introduction to calorimetry as a technique for measuring heat changes in chemical reactions.
Practical aspects of conducting calorimetric experiments and data analysis.
Hess's Law and Born-Haber Cycles:

Understanding Hess's Law and its application to determine enthalpy changes indirectly.
Introduction to Born-Haber cycles for calculating enthalpy changes in lattice energy and formation reactions.
Thermodynamic Stability and Chemical Equilibrium:

Relationship between energy changes and the stability of chemical species.
Linking energy changes to the concept of chemical equilibrium.
Energy Diagrams and Reaction Profiles:

Construction and interpretation of energy diagrams (reaction profiles) for exothermic and endothermic reactions.
Analysis of activation energy and reaction rate in relation to energy diagrams.

The Following Learning outcomes and topics are studied in the A Level Chemistry

5.1 Enthalpy change, ΔH Learning


outcomes Candidates should be able to:


1 understand that chemical reactions are accompanied by enthalpy changes and these changes can be exothermic (ΔH is negative) or endothermic (ΔH is positive)


2 construct and interpret a reaction pathway diagram, in terms of the enthalpy change of the reaction and of the activation energy


3 define and use the terms: (a) standard conditions (this syllabus assumes that these are 298K and 101 kPa) shown by ⦵. (b) enthalpy change with particular reference to: reaction, ΔHr , formation, ΔHf , combustion, ΔHc , neutralisation, ΔHneut


4 understand that energy transfers occur during chemical reactions because of the breaking and making of chemical bonds


5 use bond energies (ΔH positive, i.e. bond breaking) to calculate enthalpy change of reaction, ΔHr


6 understand that some bond energies are exact and some bond energies are averages


7 calculate enthalpy changes from appropriate experimental results, including the use of the relationships q = mcΔT and ΔH = –mcΔT/n



5.2 Hess’s Law Learning outcomes



Candidates should be able to:


1 apply Hess’s Law to construct simple energy cycles



2 carry out calculations using cycles and relevant energy terms, including:

(a) determining enthalpy changes that cannot be found by direct experiment


(b) use of bond energy data

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