1.4 Energetics Flashcards
What energy change is breaking bonds associated with?
Energy is taken in to break bonds - Endothermic Reaction
What energy change is making bonds associated with?
Energy is released to make bonds - Exothermic Reaction
What is an endothermic reaction?
Where the overall enthalpy change is positive
What is an exothermic reaction?
Where the overall enthalpy change is negative
Give an example of an endothermic reaction`
Thermal Decomposition
What is enthalpy change?
Energy change of a system at a constant pressure
What is standard enthalpy of formation?
The overall heat energy change when one mole of substance is formed from its constituent elements in their standard states at a standard temperature/pressure
What is standard ethalpy of combustion?
The overall heat energy change when 1 mole of substance is burnt completely in oxygen in standard conditions with their reactants and products in standard states.
What equation can you use to calculate enthalpy change from experimental data?
Q=mcΔT
What is Hess’s Law?
The overall heat energy change of a reaction is the same regardless of the reaction pathway taken
What is bond dissociation enthalpy?
The enthalpy change required to break a covalent bond, with all species in the gaseous state which differs for the same bond type in different molecules
Why may experimental methods for enthalpy determination not be very accurate?
- Heat is lost to surrondings
- Not in standard conditions
- Reaction may not go to completion
