lattice enthalpy, entropy Flashcards
Define lattice enthalpy
1 mole of ionic compound is formed from its gaenous ions under standard condiitons
What sign is lattice enthalpy?
-ve
Define enthalpy change of atomisation
1 mole of gaseous atoms formed from an element in its standard state
Define electron affinity
Energy change to acquire 1 mol of electrons to from 1 mol of gaseous ions
Why is the first electron affinity exothermic?
The nucleus is positive so it attracts the electron and doesn’t need energy
Why is the second electron affinity endothermic?
-Once 1st electron has been acquired, energy is needed for 2nd electron to be gained experiencing repulsion by negative charge ion
define enthalpy change of formation
-Enthalpy change to form one mole of compounds from elements in there standard state
Define enthalpy change of solution
-Enthalpy change for 1 mol of solute dissolving
Define enthalpy change of hydration
-Enthalpy change for 1 mol of gaseous ions dissolving in water
What re the 2 factors affecting lattice enthalpy?
-ionic size
-ionic charge
What element is the exception in lattice enthalpy, and explain
-Oxygen and fluorine
-O2- is more exothermic than F- because ionic charge is more significant than ionic size
Write model answer comparing NaCl and MgCl2
-Mg2+ is greater charge than Na+
-Mg2+ is smaller than Na+
-Mg2+ has a greater attraction to Cl-
-factors affecting enthalpy of hydration
-ionic size
-ionic charge
Explain the factors affecting enthalpy of hydration
-larger the ion the less attraction to water molecules
- As charge of ion increases it has a greater attraction to water molecules and becomes more exothermic
Define entropy
Entropy is a measure of the dispersal of energy in a system
