Lattice enthalpy
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Define lattice enthalpy
The enthalpy change associated with the formation of one mole of an IONIC compound from its gaseous ions under standard conditions
What is the symbol for lattice enthalpy
ΔLeHϴ
What symbol accompanies lattice enthalpy?
-
Why is lattice enthalpy always negative?
It represents the formation of bonds which releases energy and so is exothermic
Write an equation to represent the lattice enthalpy of NaCL
Na+ (g) + Cl- (g) —-> NaCl(s)
What is the definition of enthalpy of formation?
The enthalpy change that accompanies the formation of one mole of a substance from its elements under standard conditions with all reactants and products in their standard states
What is the definition of 1st ionisation energy?
The amount of energy required to remove one electron from each atom in one mole of gaseous atoms OF AN ELEMENT to form one mole of gaseous 1+ ions
Write an equation for 1st ionisation energy
Na(g) —–> Na+ (g) + e-
What is the sign of ionisation energy?
+
Why is ionisation always positive?
Energy is required to pull the electron being removed away from the nucleus
As more electrons are removed what happens to the value of IE and why?
The value increases As more electrons are removed the remaining electrons are pulled in closer to the nucleus and so more energy is required to remove the electrons
What is the definition of enthalpy of atomisation?
The enthalpy change that takes place for the formation of one mole of gaseous atoms from the element in its standard state under standard conditions
What is the sign for enthalpy of atomisation?
Always +
Why is the sign of enthaply of atomisation always +?
Bonds holding atoms together in their standard states must be broken
What is the definition of 1st electron affinity?
Th energy change that accompanies the addition of one electron to each atom in one mole of atoms of an element on gaseous form to form one mole of gaseous 1- ions
Is 1st Electron affinity exothermic?
Yes
Why is 1st electron affinity exothermic?
An electron is being added and will be attracted to the nucleus
Are subsequent electron affinities exothermic?
No
Why are subsequent electron affinities endothermic?
Electrons are being added to a negatively charged ion, and it is necessary to overcome the repulsion
From the bottom left hand side round to the bottom right hand side, what is the order of enthalpy changes?
• Formation • Atomisation • 1st ionisation energy • any subsequent ionisation energies • atomisation • 1st electron affinity • any subsequent electron affinities • lattice enthalpy
Define enthalpy of hydration
The enthalpy change when one mole of isolated gaseous ions is dissolved in water under standard conditions
Define enthalpy change of solution
The enthalpy change when one mole of a substance is completely dissolved in water under standard conditions
What is the symbol for enthalpy change of solution?
ΔsolHϴ
What is the symbol for enthalpy change of hydration?
ΔhydHϴ