5.2 - Energy
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Define the term standard lattice enthalpy
The enthalpy change when one mole of ionic lattice is formed from its gaseous ions under standard conditions
Give an example reaction equation that shows standard lattice enthalpy
Sodium ion(g) + Chloride ion(g) → NaCl(s) Calcium ion(g) + Oxygen ion (g) → CaO(s)
Define the term standard enthalpy change of formation
The enthalpy change when one mole of compound is formed from its elements in their defined standard states under standard conditions
Give an example reaction equation that shows standard enthalpy change of formation
K(s) + 1/2F2(g) → KF(s) 2C(s) + 3H2(g) + 1/2O2 (g) → C2H5OH
Define the term standard enthalpy change of atomisation
The enthalpy change when one mole of gaseous atoms is from from its elements in their defined standard states under standard conditions
Give an example reaction equation that shows standard enthalpy change of atomisation
K(s) → K(g) 1/2Br2 (s) → Br2(g)
Define the term first ionisation energy
The amount of energy required to remove one mole of electrons from one mole of gaseous atoms.
Give an example reaction equation that shows first ionisation energy
Na → Na^+ + e^- O → O^+ + e^-
Define the term second ionisation energy
The amount of energy that accompanies the formation of one mole of gaseous 2+ ions from 1 mole of gaseous 1+ iions
Give an example reaction equation that shows second ionisation energy
Na^+ → Na^2+ + e^- O^+ → O^2+ + e^-
Define the term first electron affinity
The enthalpy change that accompanies the formation of one mole of gaseous 1^- ions from gaseous atoms
Give an example reaction equation that shows first electron affinity
Cl(g) + e^- → Cl^-(g) 1/2F2(g) + e^- → F^-(g)
Define the term second electron affinity
The enthalpy change that accompanies the formation of one mole of gaseous 2^- ions from one mole of gaseous 1^- ions.
Give an example reaction equation that shows first electron affinity
Cl^-(g+ e^- → Cl^2-(g) F^-(g) + e^- → F^-(g)
What are the standard conditions
100kPa and 298Kelvin
Is Lattice Enthalpy always endothermic or always exothermic?
Always EXOTHERMIC
What factors determine lattice enthalpy?
Ionic size and Ionic charge
How does a decreasing ionic size affect lattice enthalpy?
Smaller ions have a higher charge density. This means that the ions attract to each other more strongly. Therefore, more energy is released when bonds form. Therefore, the smaller the ionic radius, the bigger the lattice enthalpy
How does an increasing ionic size affect lattice enthalpy?
Bigger ions have a smaller charge density. This means that the ions attract to each other more weakly. Therefore, less energy is released when bonds form. Therefore, the bigger the ionic radius, the smaller the lattice enthalpy
How does an increasing ionic chargevaffect lattice enthalpy?
The higher the charge on the ions, the more energy is released when an ionic lattice forms. This is due to the stronger electrostatic forces between the ions. Therefore, the higher the ionic charge, the larger the lattice enthalpy
How does a decreasing ionic charge affect lattice enthalpy?
The smaller the charge on the ions, the less energy is released when an ionic lattice forms. This is due to the weaker electrostatic forces between the ions. Therefore, the smaller the ionic charge, the smaller the lattice enthalpy
Higher lattice enthalpy means a higher or lower negative value?
Higher
What factors affect ionisation energy?
Nuclear charge Shielding Atomic radius