M5 definitions

The enthalpy change when one mole of an ionic compound is formed from its gaseous ions (used as a measure of the strength of ionic bonding).

The enthalpy change when one mole of a compound (solute) is completely dissolved in water, under standard conditions

The enthalpy change when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions, under standard conditions

A measure of the dispersal of energy in a system which is greater, the more disordered a system.

the balance between the enthalpy change (ΔH), the entropy change (ΔS) and temperature (T) for a process. ΔG = ΔH - TΔS

a reaction is feasible if ΔG < 0.

The change in concentration of a reactant or a product per unit time.

gives the relationship between the rate of reaction and the concentration of the reactants raised to the powers of their orders. E.g. for the reaction A+B –> products rate = k [A]m [B]n

‘k’ in the rate equation; the larger the value of k, the faster the reaction. k is constant at a constant temperature and increases with temperature (Arrhenius).

how the concentration of a reactant affects the rate of the reaction. In the rate equation above, Order with respect to A = m, Order with respect to B = n, Overall order = m + n

The minimum energy required for a reaction to take place, by the breaking of bonds in the reactants.

Increases the rate of a reaction without being used up by the overall reaction. It allows the reaction to proceed via a different route with lower activation energy.

Catalyst is in the same physical state as the reactants (frequently, the aqueous or gaseous state).

Catalyst has a different physical state from the reactants (frequently, reactants are gases while the catalyst is a solid).

The slowest step of a reaction mechanism of a multi-step reaction

The time taken for the concentration of a reactant to fall to half of its original concentration. (For a first order reaction, half-life is constant).

Exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change.

When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the effects of the change

For an equilibrium reaction A + B = C + D Kc = [C]c[D]d / [A]a[B]b where [] are equilibrium concentrations

For an equilibrium reaction A + B = C + D Kp = (pC)c (pD)d / (pA)a (pB)b where p are partial pressures

x(A) = number of moles of A / total number of moles in gas mixture

p(A) = mole fraction of A x total pressure P

A proton donor.

A proton acceptor.