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6968e414-66ee-4cf6-8526-9212c29d04e6 10. Sublimation of iodine. Endothermic Grade 10 SABIS SABIS

46b28dc1-97db-42e8-a04d-b46b94e24427 Potential energy diagram of an endothermic reaction. Grade 10 SABIS

1ef8152d-8c65-42b9-ab0e-3b56972744a1 Potassium reacts with hydrogen, oxygen, fluorine and chlorine to form white solids. Grade 10 SABIS

1332c7f9-0891-421e-b468-df9af5406d68 Crush some salt crystals into a powder Grade 10 SABIS SABIS Physical

6ec8ecb0-a936-41fe-9887-942cb79f66d2 Reaction of Alkali metals with chlorine. Grade 10 SABIS Generally: 2M (s) + Cl2(g) → 2MCl(s) alkali metal + chlorine → alkali metal chloride

b567f9ed-b3f8-4466-a97e-8b7ebfa59331 Law of Conservation of Matter Grade 10 SABIS SABIS Matter can never be created or destroyed. It follows that in a chemical reaction mass and atoms are conserved. As a chemical reaction involves a rearrangement of atoms number of molecules is not conserved

1e57853e-4e39-422e-9888-968a8de10e83 Phase Change The transition of a substance from one state of matter to another due to changes in temperature and/or pressure.

0f93b322-9e45-4996-86df-5b407f55e44b Filtration The process of separating a liquid from an insoluble solid by passing it through a filter, allowing the liquid to pass through while retaining the solid particles.

Exploring the Energetic World of Chemical Reactions and Thermodynamics < Back 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. Previous Next 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

731c63f0-388c-4ddc-a8bc-30a23a39d0b8 Application on Hess’s Law medium Grade 10 SABIS Question 1: Given the following reactions and their respective enthalpy changes: C(s) + O2(g) → CO2(g) ΔH1 = -393.5 kJ/mol H2(g) + 1/2O2(g) → H2O(l) ΔH2 = -286.0 kJ/mol C(s) + H2(g) → CH4(g) ΔH3 = -74.8 kJ/mol Calculate the enthalpy change for the reaction: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) Answer 1: To calculate the enthalpy change for the given reaction, we can use Hess's Law. By manipulating the given reactions, we can cancel out the common compounds and add the enthalpy changes. Multiplying reaction 1 by 2 gives: 2C(s) + 2O2(g) → 2CO2(g) 2ΔH1 = 2(-393.5 kJ/mol) = -787.0 kJ/mol Multiplying reaction 2 by 2 gives: 2H2(g) + O2(g) → 2H2O(l) 2ΔH2 = 2(-286.0 kJ/mol) = -572.0 kJ/mol Adding reactions 3, 2, and 1 gives: C(s) + H2(g) + 2H2(g) + O2(g) + 2O2(g) → CH4(g) + 2H2O(l) + 2CO2(g) ΔH3 + 2ΔH2 + 2ΔH1 = -74.8 kJ/mol + (-572.0 kJ/mol) + (-787.0 kJ/mol) = -1433.8 kJ/mol Since the given reaction is the reverse of the calculated reaction, the enthalpy change for the given reaction is the negative of the calculated value. ΔH = -(-1433.8 kJ/mol) = 1433.8 kJ/mol Question 2: Given the following reactions and their respective enthalpy changes: 2SO2(g) + O2(g) → 2SO3(g) ΔH1 = -198.2 kJ/mol S(s) + O2(g) → SO2(g) ΔH2 = -296.8 kJ/mol 2S(s) + 3O2(g) → 2SO3(g) ΔH3 = -792.0 kJ/mol Calculate the enthalpy change for the reaction: 2SO2(g) + O2(g) → 2SO3(g) + 198.2 kJ Answer 2: To calculate the enthalpy change for the given reaction, we can use Hess's Law. By manipulating the given reactions, we can cancel out the common compounds and add the enthalpy changes. Multiplying reaction 2 by 2 gives: 2S(s) + 2O2(g) → 2SO2(g) 2ΔH2 = 2(-296.8 kJ/mol) = -593.6 kJ/mol Adding reactions 1 and 2 gives: 2SO2(g) + O2(g) + 2S(s) + 2O2(g) → 2SO3(g) + 2