thermochemistry Flashcards
what does hess’s law state
enthalpy change of a reaction is independent of the route of the reaction
what is the enthalpy change formula for enthalpy change of combustion
sum of reactants - sum of products
what way do the arrows point for enthalpy of combustion
point downwards towards the elements
define enthalpy change of combustion
One mol of a substance is completely burned in oxygen under standard conditions
define enthalpy change of formation
enthalpy change when one mole of a compound is produced from its elements in their standard state
where do the arrows point in enthalpy of formation
arrows go upwards in this energy cycle because the enthalpy changes are FROM elements TO compounds
what is the equation for energy change of formation
sum of products - sum of reactants
define bond enthalpy value
the amount of energy that is needed to break a bond
define average bond enthalpy
enthalpy required to break one mole of a bond in a gaseous species under standard conditions
how to know if delta H is exothermic and endothermic
exothermic is negative
endothermic is positive
in bond enthalpies, how do you calculate delta H
sum of bonds broken - sum of bonds made
how to work out enthalpy change of a reaction
q = mcat
delta H = q/1000n (make q a minus if exothermic)
