definitions

Question 1

Rate of reaction

Answer 1

Change in concentration of a reactant or product over time

Question 2

Order

Answer 2

Power a concentration of a reactant is raised to in a rate equation, matching its stoichiometry in the RDS

Question 3

Overall order

Answer 3

The sum of all orders in the rate equation

Question 4

Rate constant

Answer 4

k in Rate = k[A]m[B]n…

Question 5

Half-life

Answer 5

Time taken for the concentration of a reactant to reduce by half

Question 6

Rate determining step

Answer 6

The slowest step in a reaction mechanism

Question 7

Mole fraction

Answer 7

Moles of gas divided by the total moles of all gases

Question 8

Partial pressure

Answer 8

Pressure from gas divided by the total pressure from all gasses

Question 9

Brønsted-Lowry acid

Answer 9

donates a proton

Question 10

Brønsted-Lowry base

Answer 10

accepts a proton

Question 11

Monobasic acid

Answer 11

one mole of acid dissociates to form one mole of H+ ions

Question 12

Dibasic acid

Answer 12

one mole of acid dissociates to form two moles of H+ ions

Question 13

Tribasic acid

Answer 13

one mole of acid dissociates to form 3 moles of H+ ions

Question 14

Buffer solution

Answer 14

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

Question 15

Oxidising agent

Answer 15

Oxidises another element, it is itself reduced

Question 16

Reducing agent

Answer 16

Reduces another element, it is itself oxidised

Question 17

Standard electrode (redox) potential, Eθ

Answer 17

The EMF of a half-cell compared to a standard hydrogen electrode under standard conditions, 298 K, 100 kPa and 1 mol dm-3

Question 18

Transition elements

Answer 18

d-block elements that have a stable ion with an incomplete d-sub-shell

Question 19

Ligand

Answer 19

A molecule or ion that can donate a lone pair to form a coordinate (dative covalent) bond to a metal ion or metal

Question 20

Bidentate ligand

Answer 20

A molecule or ion that can donate two lone pairs to form two coordinate (dative covalent) bond to a metal ion or metal

Question 21

Complex ion

Answer 21

Metal cation surrounded by coordinately bonded ligands

Question 22

Coordination number

Answer 22

Total number of coordinate bonds formed with the central metal ion

Question 23

Entropy

Answer 23

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

Question 24

which enthalpy term can be either endo or exothermic

Answer 24

enthalpy of formation and solution

Question 25

which enthalpy terms are always exothermic

Answer 25

• first electron affinity
• lattice enthalpy
• enthalpy change of hydration

Question 26

Enthalpy change of hydration

Answer 26

• Dissolving of 1 mol of gaseous ions in water, ∆hydH
• K+ (g) —-> K+ (aq)
• exothermic as water molecules surround ions to form new forces of attraction. Energy is released.

Question 27

Enthalpy change of solution
KCl

Answer 27

• Dissolving of 1 mol of solute in water, ∆solH
• KCl (s) —> K+ (aq) + Cl- (aq)
• endo/exothermic as ‘amount of heat’ released or absorbed in the dissolving process depends on whether the lattice enthalpy or hydration enthalpy is greater.

Question 28

enthalpy of atomisation, ΔatH
F

Answer 28

• ΔH when 1 mol of gaseous atoms is formed from its element
• 1/2 F2 (g) —-> F (g)
• endothermic only as energy required to break bonds between the atoms of an element.

Question 29

bond enthalpy
CF4

Answer 29

• enthalpy required to break 1 mol of a specific gaseous covalent bond
• 1/4 CF4 (g) —> 1/4 C (g) + F (g)
• endothermic only as energy required to break bonds between the atoms.

Question 30

first electron affinity ΔEA1H
Cl

Answer 30

• enthalpy released when 1 mol of gaseous atoms gains 1 mol of e- to form one mole of gaseous 1- ions
• Cl (g) + e- —> Cl- (g)
• mostly exothermic because electrostatic attraction between +ve nuclei and -ve e- formed. Can be +ve if it doesn’t form a stable ion

Question 31

second electron affinity ΔEA2H
S

Answer 31

• enthalpy released when 1 mol of 1- gaseous ions gains 1 mol of e- to form one mole of gaseous 2- ions
• S- (g) + e- —> S^2- (g)
• always endothermic as repulsion is being forced between to -ve charges
• Increased electron-electron repulsions in a dianion > the attraction of electrons to the nucleus. Electrostatic repulsion from negative ion and the electron being gained.

Question 32

lattice enthalpy, ΔLEH
NaCl

Answer 32

• ΔH when 1 mol of an ionic compound is formed from its gaseous ions
• Na+ (g) + Cl- (g) —> NaCl (s)
• always exothermic because bonds formed by ions combining, large release of energy. Ionic compound more stable than its gaseous ions.
• Strong electrostatic forces of attraction between oppositely charged ions

Question 33

Enthalpy of formation, ΔfH

Answer 33

• one mole of a compound from its constituent elements
• Na (s) + ½ Cl2 (g) —> NaCl (s) ΔHfꝋ
• endo/exothermic because:
  Bonds broken – bonds formed = overall enthalpy change

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