enthalpy change Flashcards
what is enthalpy
the absolute energy
what is enthalpy change
heat energy change measure at constant pressure standard condition all elements in their standard conditions and states
what are allotropes
THEY ARE DIFFERENT VERSIONS OF THE SAME ELEMENT when it is used can be more stable eg carbon
what is an exothermic reaction
when energy is given to the surroundings so it negative this happens when bonds are formed
what is more stable in an exothermic reaction the products or the reactants
the product r energy so are more satble
what is an endothermic reaction
when energy is taken in to break the bonds so positive
what is more stable in an endothermic reaction
the reactants as they have less energy than the products
what is enthalpy change of atomisation
enthalpy when one mol of gaseous atoms are formed from its elements in standard state
what is enthalpy of dissociation
enthalpy when one mole of covalent bond is broken to form 2 moles of its gaseous ions ( including diatomic molecules )
what is ionisation energy
enthalpy change when one mole of gaseous atoms forms one mole of gaseous ion
what is ionisation energy or endothermicq
it is endothermic as energy must be taken in to overcome the attraction between the nucleas and the electron
what is electron affinity
enthalpy change when 1 mole of gaseous ions is formed for one mole of gaseous atoms likeness for the addition of electrons
why is electron affinity exothermic
as attraction between the nucleas and the electron produce energy
what is enthalpy of formation
enthalpy change when one mol of a substance is formed from it elements in standard states and standard conditions
what is enthalpy lattice formation
enthalpy change when one mole of solid ionic compound its gaseous ions
what is lattice enthalpy dissociation
when one mole of ionic compound dissociated into its gaseous ions
why is enthalpy lattice dissociation endothermic
energy must be taken in to overcome the attraction between oppositiely charged ions
why must we use born harber cycle
as we cannot measure lattice enthalpy formation directly
why cant we measure lattice enthalpy formation directly
ass it is impossible to carry out an experiment with gaseous ions all spread out
why do ionic compounds start at the bottom
as ionic compounds intheir solid state have zero energy
