Enthalpy changes

What you'll learn

• Explain and use the term enthalpy change (∆H) and apply it to exothermic (∆H is negative) and endothermic (∆H is positive) chemical reactions
• Construct and interpret reaction pathway diagrams in terms of enthalpy changes and activation energy
• Define and use the term standard conditions
• Define and use the term enthalpy change with particular reference to enthalpy changes of reaction, formation, combustion and neutralisation
• Explain energy transfers during chemical reactions in terms of breaking and making chemical bonds
• Use bond energies to calculate enthalpy change of reaction
• Understand that some bond energies are exact and some bond energies are averages
• Calculate enthalpy changes from experimental results, including the use of the relationships: q = mc∆T and ∆H = −mc∆T
• Use Hess’s law to construct simple energy cycles
• Carry out calculations using energy cycles to determine enthalpy changes that cannot be found by direct experiment

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