CL 22- enthalpy Flashcards
lattice enthalpy
definition
the enthalpy change when 1 mol of an ionic solid is made from it’s gaseous ions under standard conditions
enthalpy change of solution
definition
the enthalpy change when 1 mol of a solute dissolves in water under standard conditions
enthalpy change of hydration
definition
enthalpy change when gaseous ions dissolve in water to form 1 mol of aqeuous ions under standard conditions
the trend in ionic charge going from group 1 to 2 to 3
- ionic charge increases
- attraction between ions increases
- lattice energy becomes more negative
- melting point increases
trend in ionic radius going down a group
- ionic radius increases
- number of shells increases
- more shielding
- nuclear attraction decreases
trend in ionic radius going across a period
- ionic radius decreases
- nuclear charge increases
- electrons are going into the same main energy level
- nuclear attraction increases
factors affecting lattice enthalpy
- ionic charge- the higher the charges on the ions, the stronger the electrostatic attractions between them, so more energy is released when forming an ionic lattice (more exothermic)
- ionic radius- the smaller the ionic radii, the larger the electrostatic attraction so the lattice enthalpy is more exothermic
factors affecting enthalpy of hydration
- ionic charge- greater charged ions are better at attracting water molecules- more energy is released when the bonds are made, giving them a more exothermic value
- ionic radius- smaller ions attract the water molecules better and have a more exothermic value
how to get a more exothermic value of lattice enthalpy
ionic charge and ionic radius
a larger ionic charge, and smaller ionic radius leads to greater attraction between ions, and a more exothermic value
how to get a more exothermic value of enthalpy of hydration
ionic charge and ionic radius
larger ionic charge, and smaller ionic radius increases the attraction for water molecules, giving a more exothermic value
