Chemical Energetics Flashcards
What does H stand for in chemical energetics?
Enthalpy - Heat energy
What does delta H stand for in chemical energetics?
Enthalpy change - amount of energy absorbed/ released in the reaction
What does Ea stand for?
Activation energy - minimum energy that colliding particles must have to react
What are the 2 things that particles need for a successful collision?
Sufficient energy
Correct orientation
What are the 2 types of reactions?
Endothermic and Exothermic
Define exothermic
Energy is transferred to the surroundings
Therefore temperature increases
Examples:
Neutralisation reactions and combustion reactions
In a energy-time graph, the products have less energy than the reactants
Delta H = negative
Define endothermic
Energy is absorbed from surroundings
Therefore temperature decreases
Examples:
Photosynthesis
Cooling packs for sports injuries
Thermal decomposition
To identify:
Heat
Is solution getting colder?
In an energy-time graph, the products have more energy than the reactants
Delta H = positive
Define bond energy
The energy required to break a bond and the energy released when new bonds form
Define bond energy rule
Bond breaking = Endothermic (Energy absorbed)
Bond making = Exothermic (Energy released)
How is delta H calculated?
Bond energy of reactants - Bond energy of products
What is the unit for bond energy?
Kilojoules per mole or KJ/mol
