5. Chem Energetics Flashcards
(14 cards)
define Standard enthalpy change of rxn, ∆H
energy change when molar qtys of reactants as stated in the thermochemical eqn react tgt under standard conditions
define Standard enthalpy change of neutralisation, ∆Hn + eqn
energy evolved when 1 mol of H₂O is formed during neutralisation of an acid and an alkali under standard conditions
∆Hn = mc∆T / n
define Standard enthalpy change of combustion, ∆Hc
energy evolved when 1 mol of substance is completely burnt in excess O₂ under standard conditions
define Standard enthalpy change of atomisation of element, ∆Hatom
energy absorbed when 1 mol of g atoms is formed from its element under standard conditions
define Standard enthalpy change of atomisation of compound, ∆Hatom
energy absorbed when 1 mol of compound is converted to its constituent g atoms under standard conditions
define bond energy
Standard bond dissociation enthalpy, ∆Hdisso
energy absorbed to break 1 mol of covalent bonds btw 2 g atoms under standard conditions
def Ionisation energy, IE
energy absorbed when 1 mol e is removed frm 1 mol of g atoms to form 1 mol of singly-charged g cations
def electron affinity, EA
energy change when 1 mol of e is added to 1 mol of g atoms to form 1 mol of singly-charged g anions
1st EA (-)
2nd EA onwards (+) to overcome repulsion btw incoming e and anion
define Lattice Energy + eqn
energy evolved when 1 mol of an ionic compound is formed from its constituent g ions under standard conditions
∝ |q₊q₋ / r₊ + r₋|
if covalent char, actual value deviate more from theoretical
def standard enthalpy of hydration, ∆Hhyd + eqn
energy evolved when 1 mol of g ions is surrounded by H₂O, forming a solution of infinite dilution under standard conditions
∝ |q/r|
Define enthalpy change of solution, ∆Hsol + eqn
energy released when 1mol of substance is dissolved by solvent such that further dilution prod no more energy change under standard conditions
∆Hsol = -LE + ∆Hhyd
define Standard enthalpy change of formation, ∆Hf
energy change when 1 mol of compound is formed from its constituent elements in their standard states under standard conditions
eqn for gibbs free energy change
∆G = ∆H - T∆S
explain ∆S
- entropy(S) inc/dec
- what happens?
(eg inc num of particles) - system changes from more to less disordered
- more ways to arrange the particles
- ∆S is +/-
