3.1.8 thermodynamics Flashcards
enthalpy change
heat energy change at constant pressure
exothermic (-ve) / endothermic (+ve)
either
enthalpy of formation
enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard states
equation for formation of water
H2(g) + 1/2 O2 (g) -> H20 (l)
exothermic (-ve) / endothermic (+ve)
mostly exothermic
enthalpy of combustion
enthalpy change when one mole of a substance undergoes complete combustion in oxygen with all substances in standard states
equation for methane
CH4 (g) + 2O2 (g) -> CO2 (g) + 2H20 (l)
equation for methane
CH4 (g) + 2O2 (g) -> CO2 (g) + 2H20 (l)
exothermic (-ve) / endothermic (+ve)
exothermic
enthalpy of neutralisation
enthalpy change when 1 mole
of water is formed in a reaction between an acid and alkali under standard conditions
exothermic (-ve) / endothermic (+ve)
exothermic
enthalpy of atomisation
enthalpy change when one mole of gaseous atoms is produced from an element in its standard state
exothermic (-ve) / endothermic (+ve)
endothermic
first ionisation energy
enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous +1 ions
equation for magnesium
Mg (g) -> Mg^+ (g) + e-
exothermic (-ve) / endothermic (+ve)
endothermic
second ionisation energy
enthalpy change when each ion in one mole of gaseous +1 ions loses one electron to form one mole of gaseous +2 ions
equation for magnesium
Mg+(g) -> Mg^2+ (g) + e-
exothermic (-ve) / endothermic (+ve)
endothermic
first electron affinity
enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions
equation for oxygen
O(g) + e- -> O^- (g)
exothermic (-ve) / endothermic (+ve)
exothermic
second electron affinity
enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions
equation for oxygen
O- (g) + e- -> O^2- (g)
exothermic (-ve) / endothermic (+ve)
endothermic (as adding -ve electron to -be ion)
lattice enthalpy of formation
enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase
equation for sodium chloride
Na+ (g) + Cl- (g) -> NaCl (s)
exothermic (-ve) / endothermic (+ve)
exothermic
lattice enthalpy of dissociation
enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase
exothermic (-ve) / endothermic (+ve)
endothermic
enthalpy of hydration
enthalpy change when one mole of gaseous ions become hydrated (dissolved in water)
equation for sodium
Na+ (g) + aq -> Na+ (aq)
exothermic (-ve) / endothermic (+ve)
exothermic
enthalpy of solution
enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and don’t interact with each other
equation for sodium chloride
NaCl (aq) + aq -> Na+ (aq) + Cl- (aq)
exothermic (-ve) / endothermic (+ve)
either
bond dissociation enthalpy
enthalpy change when one mole of covalent bonds is broken in the gaseous state
exothermic (-ve) / endothermic (+ve)
endothermic
mean bond enthalpy
enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds
exothermic (-ve) / endothermic (+ve)
either
enthalpy of vaporisation
enthalpy change when one mole of a liquid is turned into a gas
exothermic (-ve) / endothermic (+ve)
endothermic
enthalpy of fusion
enthalpy change when one mole of a solid is turned into a liquid
exothermic (-ve) / endothermic (+ve)
endothermic