Energetics Flashcards
The standard enthalpy of formation (Delta Ht)
The Enthalpy change when 1 mole of substance in its standard state is formed from its constituent elements in their standard states, under standard conditions
The standard enthalpy of combustion (Delta Hc)
The Enthalpy change when 1 mole of a substance is burnt in excess oxygen, when all quantities are measured under standard conditions.
The standard enthalpy of neutralisation
The Enthalpy change when one mole of water is formed from its ions in dilute solution under standard conditions
The standard Enthalpy of reaction
The Enthalpy change when substances react under standard conditions with the number of moles given by the equation for the reaction
Enthalpy of combustion
Products-reactants (formation enthalpies)
Enthalpy of formation
Reactants - products (combustion enthalpies)
Mean bond Enthalpy
The average energy required to break 1 mole of a covalent bond in the gaseous state under standard conditions (kjmol^-1)
Overall energy change (bond enthalpies)
= energy required to break bonds in reactants - energy released when bonds form in products
(Reactants - products)
Homogenous catalyst
A catalyst that is in the same state as the reactants and products, and provides a reaction route of lower activation energy by forming an intermediate
Heterogenous catalyst
A catalyst that is in a different state to the reactants and products, and works via chemisorption to provide a reaction route of lower activation energy
Chemisorption
The process by which reactant molecules are absorbed onto the surface of the catalyst, bonds and weakened and product molecules are desorbed from the catalyst
A homogenous system
A system in which all reactants and products are in the same physical state
Delta H
q / moles in the reaction
