F325 Definitions

Question 1

rate of reaction

Answer 1

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

Question 2

order

Answer 2

the power to which the concentration of the reactants is raised in the rate equation.

Question 3

rate constant

Answer 3

The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation.

Question 4

half-life

Answer 4

The time taken for the concentration of a reaction to reduce by half.

Question 5

rate-determining step

Answer 5

The slowest step in the reaction mechanism of a multi-step reaction.

Question 6

acid

Answer 6

Proton donor

Question 7

base

Answer 7

Proton acceptor

Question 8

acid-base pair

Answer 8

Pair of two species that transform into each other by gain or loss of electrons.

Question 9

conjugate acid

Answer 9

Species formed when a proton is added to a base.

Question 10

conjugate base

Answer 10

Species formed when a proton is added to an acid.

Question 11

buffer solution

Answer 11

A system that minimises pH changes on the addition of small amounts of acid or base.

Question 12

enthalpy change of neutralisation

Answer 12

The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of H2O(l) under standard conditions.

Question 13

lattice enthalpy

Answer 13

The energy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.

Question 14

enthalpy change of formation

Answer 14

The energy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.

Question 15

enthalpy change of atomisation

Answer 15

The energy change that takes place when one mole of gaseous atoms forms from the element in its standard state.

Question 16

first ionisation energy

Answer 16

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Question 17

first electron affinity

Answer 17

The enthalpy change that accompanies the addition of one electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.

Question 18

enthalpy change of hydration

Answer 18

The energy change that takes place when one mole of isolated gaseous ions is dissolved in water, forming one mole of aqueous ions under standard conditions.

Question 19

enthalpy change of solution

Answer 19

The energy change that takes place when one mole of a compound is completely dissociated in water under standard conditions.

Question 20

entropy

Answer 20

The quantitative measure of the degree of disorder in a system.

Question 21

standard electrode potential

Answer 21

The e.m.f of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1moldm-3 and a gas pressure of 100kPa.

Question 22

transition element

Answer 22

A d-block element which forms an ion with an incomplete d sub-shell.

Question 23

ligand

Answer 23

A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond.

Question 24

complex ion

Answer 24

A transition metal ion bonded to one or more ligands by coordinate bonds.

Question 25

coordinate number

Answer 25

The total number of coordinate bonds formed between the central metal ion and any ligands.

Question 26

bidentate ligand

Answer 26

A ligand that can donate two pairs of electrons with a transition metal ion to form two coordinate bonds.

Question 27

hydrogen-oxygen fuel cell

Answer 27

Uses energy from reaction of fuel with oxygen to create a voltage. Hydrogen half cell (H2 + 2OH- = 2H2O + 2e-) Oxygen half cell (1/2O2 + H2O + 2e- = 2OH-) Overall cell equation (H2 + 1/2O2 = H2O).