enthalpy and entropy Flashcards
What is lattice enthalpy and lattice enthalpy change? Is the value positive or negative?
Lattice enthalpy is the strength of an ionic bonding in a giant ionic lattice.
Lattice enthalpy change is the enthalpy change that accompanies the formation of one mol of an ionic compound from its gaseous ions under standard conditions.
This is formation hence it is an EXOTHERMIC reaction and the value will be negative.
What is the standard enthalpy change of atomisation? Is it an endothermic or exothermic process and why?
The standard enthalpy change of atomisation is the enthalpy change that takes place for the formation of one mol of gaseous ions from the elements under standard conditions.
Since the elements are changed from standard conditions to gaseous ions, this is an endothermic reaction as it involves bond breaking ( produces negative values ).
What is the first ionisation energy and is it an endothermic or exothermic process?
The first ionisation energy is the energy required to remove one electron from each atom in one mol of gaseous atoms to form one mol of gaseous 1+ ions.
This process is an endothermic reaction, the value will be positive, as energy is required to overcome the attraction between the electron and nucleus.
What does it mean by the first electron affinity and is it an endothermic or exothermic process?
The first electron affinity is the enthalpy change that takes place when one electron is added to each atom in one mol of gaseous ions to form one mol of gaseous -1 ions.
This process is exothermic as an electron is being added so the value will be negative.
What are the three processes required to form an ionic lattice?
1) Formation of gaseous atoms
Changing elements from their standard states into gaseous atoms
2) Formation of gases ions
Changing gaseous atoms into positive or negative ions
3) Lattice formation
Changing gaseous ions into an ionic lattice
Why are second electron affinities endothermic?
Second electron affinities are endothermic as a second electron is being obtained by a negative ion which would usually repel hence energy is needed to be put in to work against the repulsion.
What is the enthalpy change of solution? Is the value endothermic or exothermic?
The enthalpy change associated with the dissolving process.
It occurs when one mol of a solute dissolves in a solvent, and if the solvent is H2O, the ions from the ionic lattice finish up by being surrounded by H2O molecules as aqueous ions.
This can be both endothermic and exothermic dependent on the lattice enthalpy and enthalpy change of hydration.
What are the two stages associated with a solid ionic compound being dissolved in water?
1) The ionic lattice is broken up to form separate gaseous ions, this is the opposite of the lattice enthalpy as instead of an ionic compound being formed, it is being broken into its gaseous ions.
2) The gaseous ions interact with polar water molecules to form hydrated aqueous ions. This is the enthalpy change of hydration.
What is the enthalpy change of hydration?
The enthalpy change of hydration is the enthalpy change that accompanies the dissolving of gaseous ions in water to form one mol of gaseous ions.
How does ionic size affect lattice enthalpy and hydration?
As ionic size increases, the attraction between the ions decrease, lattice enthalpy and enthalpy change of hydration become less negative and melting point decreases.
How does ionic charge affect lattice enthalpy and enthalpy change of hydration?
As ionic charge increases, the attraction between the ions increase, lattice enthalpy will become more negative and melting point increases.
