Definitions

Question 1

Define: Enthalpy change

Give the symbol

Answer 1

Heat energy change measured under conditions of constant pressure.

Question 2

Define: Standard enthalpy of combustion

Give the symbol

Answer 2

The enthalpy change when one mole of a substance is burnt completely in oxygen in standard conditions. All reactants and products are in their standard states.

Question 3

Define: Standard enthalpy of formation

Give the symbol

Answer 3

The enthalpy change when one mole of a compound is formed from its constituent elements in standard conditions. All products and reactants are in their standard states.

Question 4

Define: Mean bond enthalpy

Answer 4

The enthalpy change when one mole of covalent bonds in a gaseous molecule are broken. It is an average over many different molecules.

Question 5

State Hess’ Law

Answer 5

The enthalpy change for a reaction is independent of the route taken from reactants to products.

Question 6

Define: Hetereogenous catalyst

Answer 6

A catalyst that is in a different phase to the reactants.

Question 7

Define: Homogenous catalyst

Answer 7

A catalyst that is the same phase as the reactants.

Question 8

Define: Activation energy

Answer 8

The minimum energy required for a reaction to occur.

Question 9

Define: Transition state

Answer 9

The species at the top of the curve on an enthalpy level diagram

Question 10

Define: Rate of reaction

Answer 10

Change in concentraion per unit time.

Question 11

Define: Dynamic Equilibrium

Answer 11

Rate of forward reaction = Rate of backward reaction

Concentrations of reactants and products are constant

Question 12

Define: Catalyst

Answer 12

A substance that provides an alternative reaction pathway of lower activation energy.

OR

A substance that increase the rate of reaction and is chemically unchanged when the reaction has finished.

Question 13

Define: Disproportionation reaction

Answer 13

A reaction where the same species is both oxidised and reduced.

Question 14

Define: Polymerisation

Answer 14

Joining monomers to form long chains.

Question 15

Define: Carbon neutral

Answer 15

An activity where there is no net carbon emissions to the atmosphere.

Question 16

Define: Elastic collision

Answer 16

Collisions in which energy is transferred between molecules but no energy is lost.

Question 17

Define: Hydration

Answer 17

Addition of water to a molecule.

Question 18

Define: Hydrolysis

Answer 18

Breaking of a molecule by addition of water.

Question 19

Define: Molecular ion

Answer 19

The molecule with a single positive charge.

Question 20

State Le Chatlier’s Principle

Answer 20

When a system is in equilibrium, the position of equilibrium will shift such as to oppose the change introduced to the system.

Question 21

Define: Brønsted-Lowry acid

Answer 21

Proton donor

Question 22

Define: Brønsted-Lowry base

Answer 22

Proton acceptor

Question 23

Define: Buffer solution

Answer 23

A solution that is resistant to changes in pH when small amounts of acid/alkali are added

Question 24

Define: Structural isomerism

Answer 24

Same molecular formula but different structural formula

Question 25

Define: Stereoisomerism

Answer 25

Same **structural** formula but different arrangement of atoms in space

Question 26

Define: Complex ion

Answer 26

Central metal ion surrounded by ligands

Question 27

Define: Ligand

Answer 27

Electron pair donor which forms **coordinate bond(s)** with a central metal ion

Question 28

Define: Coordination number

Answer 28

The number of **coordinate bonds** to the central metal ion

Question 29

Define: Lewis acid

Answer 29

Electron pair acceptor

Question 30

Define: Lewis base

Answer 30

Electron pair donor

Question 31

# Define: Lattice enthalpy of dissociation Give the symbol

Answer 31

The enthalpy change when **one mole** of a compound is from from its **gaseous ions**.

Question 32

# Define: Lattice dissociation enthalpy Give the symbol

Answer 32

The **enthalpy change** when **1 mole** of a compound is **comp****letely dissociated**into its**gaseous ions**.

Question 33

# Define: Enthalpy of atomisation Give the symbol

Answer 33

The **enthalpy change** when **1 mole** of **gaseous atoms** are from a substance in its standard state.

Question 34

# Define: First ionisation energy Give the symbol

Answer 34

The **enthalpy change** when **1 mole** of electrons are removed from **1 mole** of **gaseous atoms** to form **1 mole** of **gaseous ions** with a **single postive charge**.

Question 35

# Define: First electron affinity Give the symbol

Answer 35

The **enthalpy change** when **1 mole** of electrons are added to **1 mole** of **gaseous atoms** to form **1 mole** of **gaseous ions** with a **single negative charge**.

Question 36

# Define: Enthalpy of hydration Give the symbol

Answer 36

The **enthalpy change** when **one mole** of **gaseous ions** are dissolved in water to form **one mole** of **aqueous ions**.

Question 37

# Define: Enthalpy of solution Give the symbol

Answer 37

The **enthalpy change** when **one mole** of a compound is dissolve in suffient solvent such that there is **no further enthalpy change**.