Enthalpy Flashcards
enthalpy change equation
products - reactants
enthalpy change of formation equation
products - reactants
enthalpy change of combustion equation
reactants - products
bond enthalpy equation
reactants - products
what is an exothermic change?
from system to surroundings (temp rise) (energy fall)
what is an endothermic change?
from surroundings to system (temp falls) (energy rise)
what is activation energy?
minimum energy required for a reaction to take place
what are standard conditions?
100kPa pressure
298K temperature
1mol/dm^-3 concentration
what is enthalpy change of reaction?
enthalpy change which follows a reaction in the molar quantities shown in a chemical equation under standard conditions
what is enthalpy change of formation?
enthalpy change when 1 mole of a compound is formed from its elements under standard state and conditions
what is enthalpy change of combustion?
enthalpy change when 1 mole of a compound reacts completely with oxygen under standard state and conditions
what is enthalpy change of neutralisation?
energy change when 1 mole of water is formed after a reaction between a base and an acid under standard state and conditions
what could effect the accuracy of an experimental value of ∆cH?
- heat loss to surroundings
- incomplete combustion has occurred
- evaporation of methanol
- was not done under standard conditions
what is the average bond enthalpy?
energy required to break one mole of a specified type of bond in a gaseous molecule
why are bond enthalpies always endothermic?
energy is needed to break bonds
therefore bond enthalpies always have a +ve value
