Enthalpy Changes Flashcards
Explain the law of conservation
The amount of energy in an isolated system remains the same. Energy cannot be destroyed or created =, it can only be transferred from one to another
What energy change is breaking bonds associated with
Energy is taken in to break bonds
Endothermic reaction
What energy change is associated with making bonds
What energy is released to make bonds
exothermic reaction
What is an endothermic reaction
A reaction with an overall positive enthalpy change
Enthalpy products > enthalpy of reactants
What is an exothermic reaction
A reaction with an overall negative enthalpy change
enthalpy of products < enthalpy of reactants
Define activation energy
The minimum energy required for a reaction to take place
What are standard conditions
100KPa
298K
Define enthalpy change of formation
The energy change that takes place when 1 mole of a compound is formed from its elements in their standard state under standard conditions
Define enthalpy change of combustion
The energy change that takes place when 1 mole of a substance is completely combusted with oxygen
Define enthalpy change of neutralisation
the energy change that takes place when 1 mole of water is formed from a neutralisation reaction
What does enthalpy change of reaction mean
The energy change associated with a given reaction
What is the equation for calculating enthalpy change
q = mc∆T
What are the advantages of using a bomb calorimeter
Minimises heat loss
Pure oxygen used, ensures complete combustion
Why might experimental methods for enthalpy determination not be accurate
Heat is lost to the surroundings
Not in standard conditions
reaction may not go to completion
What does average bond enthalpy mean
the mean energy required to break 1 mole of bonds in gaseous molecules
