Bond Enthalpies (OCR A-Level Chemistry A): Flashcards

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Bond Enthalpies
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Average bond enthalpy definition

Energy to break 1 mole of a bond type in gaseous molecule

Bond breaking: endothermic or exothermic?

Endothermic - requires energy input

Sign of ΔH\Delta H for bond breaking

Positive (endothermic process)

Sign of ΔH\Delta H for bond making

Negative (exothermic, energy released)

Relative strength: triple, double, single bonds

Triple > double > single (higher bond enthalpy)

Formula for ΔrH\Delta_r H using bond enthalpies

ΔrH\Delta_r H = bonds broken - bonds made

Why bond enthalpies are 'average' values

They vary with chemical environment/molecular structure

State requirement for bond enthalpy calculations

All species must be gaseous molecules

When is a reaction exothermic overall?

When bond making releases more energy than bond breaking needs

Sign of bond enthalpy values

Always positive (breaking bonds is endothermic)

Explore OCR A-Level Chemistry A Revision Notes by Topics

Periodicity

Reactivity Trends

Enthalpy

Reaction Rates and Equilibrium

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Periodicity

Reactivity Trends

Enthalpy

Reaction Rates and Equilibrium

Explore OCR A-Level Chemistry A Quizzes by Topics

Periodicity

Reactivity Trends

Enthalpy

Reaction Rates and Equilibrium

Explore OCR A-Level Chemistry A Exam Questions by Topics

Periodicity

Reactivity Trends

Enthalpy

Reaction Rates and Equilibrium

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