AQA Chemistry - Thermodynamics

The standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions.

The standard enthalpy change when one mole of solid ionic compound dissociated into its gaseous ions.

The enthalpy change when one mole of a compound is formed from its elements in their standard states, under standard conditions

Enthalpy change when one mole of electrons is removed from one from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Enthalpy change when one mole of electrons is removed from one mole of gaseous atoms 1+ ions to form one mole of gaseous 2+ ions

The enthalpy change for a reaction is independent of the route taken.

Zero by definition

The enthalpy change that takes place when one mole of a substance is completely burnt in (excess) oxygen

Enthalpy change when one mole of gaseous atoms is formed from a compound in it's standard state under standard conditions

Enthalpy change when one mole of gaseous atoms gains one mole of electrons to form one mole of gaseous 1- ions

Enthalpy change when one mole of gaseous 1- ions gains one mole of electrons to form one mole of gaseous 2- ions

Enthalpy change when one mole of gaseous ions become hydrated/dissolved in water to infinite dilution (water molecules totally surround the ion)

Enthalpy change when one mole of covalent bonds is broken, with all species in the gaseous state.

Thermochemical cycle showing all the enthalpy involved in the formation of an ionic compound. Start with elements in their standard states (enthalpy of 0)

Size of the ions, charge on the ions

Enthalpy change when one mole of solute dissolves completely in a solvent to infinite dilution

Assumes that ions are perfectly spherical and that there is an even charge distribution (100% polar bonds). Act as point charges.

Polarisation often occurs when small positive ions or large negative ions are involved, so the ionic bond gains covalent character. Some lattices are not regular and the crystal structure can differ.

Between large positive ions and small negative ions.

Reaction does not take account of rate of reaction.

Negative - exothermic

Disorder of a system. Higher value for entropy = more disordered

JK-1mol-1

Entropy always increases, as it's overwhelmingly more likely for molecules to be disordered than ordered.

Positive - reactions always try and increase the amount of disorder

Entropy change = sum of products' entropy - sum of reactants' entropy

Smaller ions, as the charge centres will be closer together. Increased charge, since there will be a greater electrostatic force of attraction between the oppositely charged ions. Increasing the charge on the anion has the effect of increasing ionic size which has a smaller effect than increasing the charge on a cation.

∆G = ∆H - T∆S

-change in Gibbs Free Energy = ∆G -change in enthalpy = ∆H -temperature in Kelvin = T -change in entropy = ∆S

This is the temperature (in kelvin) at which the reaction becomes feasible

T = ∆H/∆S Since G=0

Gibbs free energy only indicates if a reaction is feasible. It does not take into account the rate of reaction. Many reactions that are feasible at a certain temperature have a rate of reaction that is so slow that effectively no reaction is occuring.

G is always negative, so reaction always feasible - product favoured

G is always positive, so reaction is never feasible - reactant favoured

Temperature dependent

Temperature dependent

No disorder - molecules/atoms are not moving or vibrating and cannot be arranged in any other way. Maximum possible state of order

-Number of moles - more moles made = increases in entropy -Going from solid = liquid/gas or liquid = gas

The heat is given out escapes to the surroundings