Thermodynamics Flashcards
Metals and non metals form:
Ionic compounds
Definition of lattice enthalpy of formation:
The enthalpy change when one mole of crystalline/solid ionic substance is formed from its constituent ions in their gaseous state under standard conditions.
Definition of lattice dissociation enthalpy:
The enthalpy change when one mole of crystalline/solid ionic substance breaks into its smaller constituent ions in their gaseous state under standard conditions.
Definition of first ionisation energy:
The enthalpy change when one mole of gaseous atoms loses one electron per atom under standard conditions.
Definition of second ionisation energy:
The enthalpy change when one mole of gaseous +1 ions lose one electron per atom under standard conditions
Definition of first electron affinity enthalpy:
The enthalpy change when one mole of gaseous atoms gains one electron per atom under standard conditions.
Definition of second electron affinity enthalpy:
The enthalpy change when one mole of gaseous -1 ions gain an electron per atom under standard conditions.
Definition of hydration enthalpy:
The enthalpy change when one mole of gaseous ions become hydrated or aqueous.
Definition of enthalpy of solution:
The enthalpy change when one mole of an ionic solid dissolved into enough water to completely separate all the ions.
Definition of enthalpy of formation:
The enthalpy change when one mole of a substance is formed from its constituent elements in their standard states under standard conditions.
Definition of enthalpy of combustion:
The enthalpy change when one mole of a substance is completely combusted in oxygen in their standard states under standard conditions.
Definition of enthalpy of atomisation of an element:
The enthalpy change when one mole of gaseous atoms are produced from one mole of standard state elements.
Definition of enthalpy of bond dissociation:
Enthalpy change when one mole of a covalent bond is broken in the gaseous state.
What is entropy?
The measure of dissociation.
What is entropy measured in?
JK^1mol^1 has the symbol S
🔺S total =
🔺S reaction - 🔺S surroundings
🔺S reaction =
🔺S products - 🔺S reactants
Definition of enthalpy change of atomisation in a compound:
The enthalpy change when 1 mole of a compound in its standard state is converted to its gaseous atoms.
Exothermic thermic reactions have a … value
Exothermic reactions have a negative value, because heat energy is given out.
Endothermic reactions have a … value
Endothermic reactions have a positive value, because heat energy is absorbed.
In order for a reaction to be feasible 🔺G must be:
Must be negative or zero.
Equation to calculate 🔺G:
🔺G = 🔺H - T🔺S
How does feasibility depend on temperature?
If H is positive and S is positive than the reaction would be feasible at some temperatures but will be at a high enough temperature.
If H is negative and S is negative then the reaction will be feasible at lower temperatures but not visible at higher temperatures.
If H is positive and S is positive and G is negative the reaction will be feasible at any temperature
If H is positive and S is negative than G is positive the reaction ISN’T feasible.
