Topic 8,13 - Energetics Flashcards
(21 cards)
Enthalpy change
Heat energy change at constant pressure.
Standard conditions
100 kPa, 298 K, 1 moldm⁻³.
Exothermic
Releases heat; negative enthalpy change.
Endothermic
Absorbs heat; positive enthalpy change.
Standard enthalpy change of reaction
Change under standard conditions for molar quantities.
Standard enthalpy change of formation
Formation of 1 mole of a compound from elements.
Standard enthalpy of combustion
Burning 1 mole in oxygen.
Standard enthalpy of neutralisation
Reaction of acid and alkali to form 1 mole water.
Equation for calorimetry
Q = mCΔT.
Specific heat capacity
Energy needed to raise temperature of 1 g by 1°C.
Hess’s law
Total enthalpy change is path-independent.
Bond Enthalpy
Energy to break 1 mole of a bond in gas phase.
Mean bond enthalpy
Average energy to break a specific bond across molecules.
Standard lattice energy
Energy change when 1 mole of an ionic solid is formed from its gaseous ions under standard conditions.
Standard enthalpy of atomisation
Enthalpy change when 1 mole of gaseous atoms is formed from the elements in standard states.
First electron affinity
Enthalpy change when one electron is added to each atom in 1 mole of gaseous atoms.
Enthalpy change of hydration
Enthalpy change when 1 mole of gaseous ions is dissolved in water.
Enthalpy change of solution
Enthalpy change when 1 mole of ionic solid dissolves in water to form an infinitely dilute solution.
Polarisation
Distortion of charge distribution in a molecule, leading to covalent character in ionic compounds.
Entropy
Measure of disorder of a system.
Gibbs free energy
Measure of reaction feasibility: ΔG = ΔH – TΔS. Reaction is spontaneous if ΔG < 0.
