Thermodynamics Flashcards
(19 cards)
Enthalpy of neutralisation (exo)
Enthalpy change when 1 mole of water is formed in a reaction between an acid and alkali under standard conditions
electron affinity (exo)
First electron affinity = enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions.
Enthalpy of atomisation (endo)
Enthalpy change when one mole of gaseous atoms is produced from an element in its standard state.
Hydration enthalpy (exo)
Enthalpy change when one mole of gaseous ions become hydrated (dissolved in water).
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.
Bond dissociation enthalpy (endo)
Enthalpy change when one mole of covalent bonds is broken in the gaseous state.
Lattice enthalpy of formation (exo)
Enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions
Lattice enthalpy of dissociation (endo)
Enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase
Enthalpy of vaporisation (endo)
Enthalpy change when one mole of a liquid is turned into a gas
Enthalpy of fusion (endo)
Enthalpy change when one mole of a solid is turned into a liquid
Explain why the theoretical enthalpy of lattice dissociation for … is different from
The experimental value calculated using born haber cycle
- Experimental lattice enthalpy value includes covalent interactions
- Theoretical lattice enthalpy value assumes only ionic interaction exist
In terms of electrostatic forces, suggest why the electron affinity of fluorine has a negative value.
There is an attraction between the nucleus / protons and (the added) electron(s) Energy is released (when the electron is gained)
The first ionisation energy of sodium is more endothermic than that of potassium explain why
Sodium has a smaller atomic radius
Electrons experience more attraction
The lattice enthalpy of sodium oxide is more exothermic than that of potassium oxide expain why.
Ionic radius of sodium is smaller
Na+ has a stronger attraction to 02-
What does the lattice enthalpy indicate?
the strength of the ionic bonding
the greater the magnitude of the lattice enthalpy the stronger the bonding
How would the lattice enthalpies of magnesium chloride and calcium chloride differ?
• Lattice enthalpy of MgCl2 is more exothermic than CaCl2
• therefore the attraction between Mg2+ and Cl- is greater
Explain why it is difficult to predict whether the lattice enthalpy of magnesium sulfide would be more or less exothermic than the lattice enthalpy of sodium oxide.
•comparison of size AND charge of cations
•comparison of size of Anions
•comparison of attraction of a cation AND an anion
State why the values of H is positive for the change of state of carbon dioxide from solid to gas.
Intermolecular forces need to be overcome
State why x has zero entropy at a temperature of 0k
No disorder
