THERMODYNAMICS HAVENT FINISHED

What is the definition of the enthalpy change of formation of a compound?

the energy transferred when 1 mole of the compound is formed from its elements under standard conditions where all the reactants and products are in their standard states

What is the definition of the enthalpy of atomisation?

the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard states

What is the definition of the enthalpy of sublimation?

the enthalpy change of a solid metal turning to gaseous atoms and will numerically be the same as the enthalpy of atomisation

What is the definition of the bond dissociation enthalpy?

the standard molar enthalpy change when 1 mole of a covalent bond is broken into 2 gaseous atoms

\\what is the bond enthalpy of dissociation for diatomic molecules?

2x the atomisation energy of the element

What is the definition for the first ionisation energy?

the enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a +1 charge

What is the definition of the second ionisation energy?

the enthalpy change to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to produce 1 mole of gaseous 2+ ions

What is the definition of the first electron affinity?

• enthalpy change that occurs when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a -1 charge

• exothermic for atoms that normally form negative ions

What is the definition for the second electron affinity?

• enthalpy change when one mole of gaseous 1- ions gains 1 electron per ion to produce gaseous 2- ions

• endothermic as it takes energy to overcome the repulsive force between the negative ion and the electron

What is the definition of the enthalpy of lattice formation?

the standard enthalpy change when 1 mole of an ionic crystal lattice is formed from its constituent ions in gaseous form

What is the definition of the enthalpy of lattice dissociation?

standard enthalpy change when 1 mole of an ionic crystal lattice form is separated into its constituent ions in gaseous form

What is the definition of the enthalpy of hydration?

• enthalpy change when 1 mole of gaseous ions becomes aqueous ions

• exothermic as bonds are made between the ions and water molecules

What is the definition of the enthalpy of solution?

• standard enthalpy change when 1 mole of an ionic solid dissolves in a large enough amount of water to ensure that the dissolved ions are well separated and do not interact with onne another

What is the born-haber cycle of sodium chloride?

What does the strength of the enthalpy of lattice formation depend upon?

• the sizes of the ions (larger ions means that they’re less negative)

• charges on the ion (bigger the charge, the greater the attraction between ions)

What is the perfect ionic model?

ions are 100% ionic and spherical and attractions are purely electrostatic

When is there usually a tendency towards covalent character in ionic substances?

• positive ion is small

• positive ion has multiple charge

• negative ion is large

• negative ion has multiple negative charges

Why is there usually differences between theoretical and born haber lattice enthalpies?

• the compound may show covalent character meaning the theoretical and born haber lattice enthalpies differ

• the more covalent character the bigger the difference between the values

What happens to the theoretical value compared to the Born-haber value if a compound has covalent character?

• tends towards giant covalent

• lattice is stronger

• charge cloud is distorted

• born-haber would be larger than theoretical value

What happens when the negative ion becomes more covalent?

• becomes distorted and polarised

• metal cation is polarising the negative ion

What is a spontaneous process?

proceeds on its own without any external influence

What is the problem with an exothermic reaction?

• produces products that are more thermodynamically stable

• causes them to be spontaneous

What is entropy?

• a description of the number of ways atoms can share quanta of energy

• the higher the entropy the more ways the substances have to arrange their atoms and the more disordered energy there is

What do elements, simpler compounds and purer substances tend to have lower entropies than?

compounds, complex compounds and mixtures