Topic 19- Thermodynamics Flashcards
Enthalpy of formation
The enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
Mean bond enthalpy
The enthalpy change when one moles of covalent bonds is broken, with all species in the gaseous state, averaged over a range of different compounds.
Enthalpy change of atomisation of an element
The enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state
Enthalpy change of atomisation of a compound
The enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms
First ionisation energy
The enthalpy change when 1 mole of gaeous 1+ ions is formed from 1 mole of gaseous atoms
Second ionisation enthalpy
The enthalpy change when one mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions
First electron affinity
The enthalpy change when 1 mole of gaseous 1- ions are formed from 1 mole of gaseous atoms
Second electron affinity
The enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions
Enthalpy change of hydration
The enthalpy change when water molecules surround one mole of gaseous ions
Enthalpy of solution
The enthalpy change when 1 mole of an ionic solid dissolves completely in sufficient water to form a solution in which the ions are far enough apart not to interact with each other.
Lattice enthalpy of formation
The enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions
Lattice enthalpy of dissociation
The enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions under standard conditions
Why do theoretical lattice enthalpies differ from experimental values
Due to covalent character
What indicates how close a compound is to the perfect ionic structure?
The difference between experimental and theoretical lattice enthalpy values
What indicates how close a compound is to the perfect ionic structure?
The difference between experimental and theoretical lattice enthalpy values
When do substances tend to dissolve?
When it is neutral or exothermic
When do substances tend to dissolve?
When enthalpy of solution is neutral or exothermic
Equation to calculate entropy
Change in entropy= Entropy of products- Entropy og reactants
Equation for free energy change
Delta G=Delta H-T *Delta S
What are the units of free energy change?
J/mol
Feasibility of reaction: Exothermic and positive entropy
Feasible at all temperatures
Feasibility of reaction: Exothermic and negative entropy
Below certain temperatures
Feasibility of reaction: Endothermic and positive entropy
Above certain temperatures
Feasibility of reaction: Endothermic and negative entropy
Feasible at no temperatures
Explain why enthalpy of hydration becomes less exothermic down group 1
Lower charge density down group
Attraction between partially negative oxygen and metal ion lower
