3.1.8 Thermodynamics Flashcards
What is enthalpy?
a measure of the heat content of a substance
What is enthalpy change (△H) and (ΔHϴ)?
change in heat content at constant pressure
enthalpy change measured under standard conditions - 100kPa and 25C
What is Standard Enthalpy of Formation? exo or endo
1 mole of a substance is formed from its constituent elements in standard states under standard conditions
Exothermic
What is Standard enthalpy change of combustion? exo/endo
1 mole of a substance is completely burned in oxygen in standard states under standard conditions
Exothermic
What is standard enthalpy change of neutralisation? exo/endo
1 mole of water is formed in a reaction between an acid and alkali under standard conditions
Exothermic
What is Hess’s Law?
the enthalpy change for a reaction is independent of the route taken
How to work out enthalpy change of formation?
sum of △fH products - sum of △fH reactants
Heat energy equation.
q = mc△T
number of moles
What is first ionisation energy? exo/endo
enthalpy change when each atom in one mole of gaseous atoms loses one election to form one mole of gaseous 1+ ions
Endothermic
What is second ionisation energy? exo/endo
enthalpy change when each atom in one mole of gaseous 1+ ions loses one election to form one mole of gaseous 2+ ions
Endothermic
What is first election affinity? exo/endo
enthalpy change when each ion in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions
Exothermic
What is second electron affinity? exo/endo
enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions
Endothermic
What is enthalpy of atomisation? exo/endo
one mole of gaseous atoms is produced from an element in its standard state
Endothermic
