energetics Flashcards
(17 cards)
What is the enthalpy change of formation?
-enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard states under standard conditions.
what is first ionisation enthalpy?
-enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions.
what is first electron affinity?
enthalpy change when each atom in mole of gaseous atoms gains one electrons to form one mole of gaseous 1- ions.
what is enthalpy of atomisation?
enthalpy change when one mole of gaseous atoms is produced from an element in its standard state.
what is hydration enthalpy?
enthalpy change when one mole of gaseous ions is dissolved in water.
is atomisation exo or endothermic?
endothermic
what is enthalpy of solution?
enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other.
what is bond dissociation enthalpy?
enthalpy change when one mole of covalent bonds is broken ion gaseous state.
what is lattice enthalpy of formation?
enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase.
what is lattice enthalpy of dissociation?
-enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in gas phase.
what is enthalpy of vaporisation?
enthalpy change when one mole of a liquid is turned into a gas
what is enthalpy of fusion?
enthalpy change when one mole of a solid is turned into liquid.
what is meant by lattice energy?
-lattice energy is the energy released when one mole of an ionic compound is formed in its standard state from its ions in their gaseous states.
explain the effect of ionic charge and ionic radius on the magnitude of the lattice energy of an ionic compound?
lattice energy is more exothermic with increasing charge on the ions and decreasing the size of the ions.
the greater the charge on the ions,the larger the electrostatic forces of attraction between the oppositely charged ions in the lattice.
the smaller the ions the smaller the inter-ionic distance and the greater the forces of attraction.
why is the second electron affinity always endothermic?
-because it takes energy to overcome the repulsive force between the negative ion and the electron.
state the trend in the first electron affinities down group 7?
-they become less exothermic (less negative) since the atoms get bigger and have more shielding so it becomes less easy to attract electrons to the atom to form the negative ion. (stronger attraction more energy released)
difference between experimental and theoretical lattice energy values?
experimental- determined using born-haber cycles and is the real value
theoretical - determined using mathematical calculations that assume the ions are in contact with each other, the ions are purely spherical and that the each ion can be considered as a point charge.
