Paper 5 Flashcards
Rate =
k[A]m[B]n
Can on,y be determined practically by experiment
Rate of reaction
The change in conc of a reactant or product per unit time
Overall order
M+n
Half life
The time taken for the concentration of a reactant to reduce by half
Initial rate
The rate right at the start of a reaction (t=0)
Rate determining step
The slowest step in the mechanism of a multi-step reaction
An intermediate
Used up in one step of the reaction and formed in a subsequent step. Not seen as a product or reactant in the overall equation.
Kc=
[prod]/[react]
pH=
-log[H+]
pKa=
-logKa
[H+]=
10^-pH
Ka=
10^-pKa
Ionic product of water (Kw)
Kc = [H+][OH-]/[H2O]
Eq to left so v small
Kc x [H2O] = Kw = [H+][OH-]
Buffer
A solution able to oppose changes in pH when small quantities of acid or base are added
(Weak acid and conjugate base)
Enthalpy of neutralisation
The enthalpy change when an aqueous acid reacts with an aqueous base to form 1 mole of water under standard conditions (100kPa, 298K)
Equivalence point
The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution matching the stoichiometric of the reaction
Hess’ Law
States that if a reaction can take place by more that one route and the initial and final conditions and the same, the total enthalpy change is the same for each route.
Lattice enthalpy (LE)
The enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions (298K, 100kPa).
e.g. K+(g) + Cl-(g) ➡️ KCl(s)
Standard enthalpy change of formation (
The enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard States under standard conditions (298K, 100kPa)
e.g. K(s) + 1/2Cl2(g) ➡️ KCl(s)
-
Standard enthalpy change of atomisation (
The enthalpy change when 1 mole of gaseous atoms forms from the elements in their standard states under standard conditions (298K, 100kPa)
e.g. 1/2Cl2(g) ➡️ Cl(g)
+
First ionisation energy (
The enthalpy change when 1 electron is removed from each atoms in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
e.g. Cl(g) ➡️ Cl+(g) + e-
Second ionisation energy (
The enthalpy change when 1 electron is removed from each ion in 1 mole of 1+ gaseous ions to form 1 mole of gaseous 2+ ions.
e.g. Ca+(g) ➡️ Ca2+(g) + e-
First electron affinity (
The enthalpy change when 1 electron is added to each atom in 1 mo,e of gaseous atoms forming 1 mole of gaseous 1- ions.
e.g. Cl(g) + e- ➡️ Cl-(g)
-
Second electron affinity (
The enthalpy change when 1 electron is added to each ion in 1 mole of gaseous 1- ions forming 1 mole of gaseous 2- ions.
e.g. O-(g) + e- ➡️ O2-(g)
+
Born-Haber cycles
Used to calculate enthalpy change that cannot be measured direct,y.
Standard enthalpy change of solution (
The enthalpy change when 1 mole of a compound is fully dissolved in water under standard conditions (298K, 100kPa)
e.g. KCl(s) ➡️ K+(aq) + Cl-(aq)
+/-
Standard enthalpy change of hydration (
The enthalpy change when 1 mole of aqueous ions are formed from gaseous ions under standard conditions (298K, 100kPa).
e.g. K+(g) + aq ➡️ K+(aq)
+
Standard entropy change of a reaction (
The entropy change of a reaction in the molar quantities expressed in th equation under standard conditions (298K, 100kPa) in standard States.