Enthalpy Changes Flashcards
What is enthalpy
Measure of heat energy inside of a system
Enthalpy change?
ΔH = H(products)- H(reactants)
What is the law of conservation of energy
Energy can neither be created nor destroyed only transferred
Exothermic reactions
heat from the system is transferred to the surroundings
Endothermic reactions
heat from the surroundings is transferred the the system
What is activation energy
The energy input needed to break bonds to start a reaction
What are standard enthalpy conditions
standard condiitions for enthalpy reactions
pressure:100kpa
temperature:298k
concentration: 1 moledm-
definition of enthalpy change of combustion
enthalpy change when 1 more of a substance reacts with oxygen under standard conditions with all the reactants and products un their standard states
definition of enthalpy change of formation
enthalpy change when 1 mole of a compound is formed from is elements under standard conditions with reactants and products in their standard states
definition of enthalpy change of neutralisation
energy change that accompanies the reaction of a base to form 1 mole of h20 under standard conditions with reactants and products in their standard states
ΔH?
ΔH= MCT
How may there be a loss of accuracy in enthalpy change reactions
-incomplete combustion may take place
-evaporation of methanol use of cover to reduce the error
-standard conditions required some reactions are not taken in standard conditions
What is average bond enthalpy
energy required to break one mole of a type of bond in a gaseous moleccule
What does hess law state
if a reaction takes place by two routes and start and finish in the same place with the same conditions the total enthalpy change is the same for each route
What is an exothermic reaction in terms of bonds
when more energy is required making bonds than breaking them
