Definitions

Question 1

Electronegativity

Answer 1

The power of an atom to attract electron density in a covalent bond towards itself.

Question 2

Activation energy

Answer 2

Minimum energy that a particle needs in order to react.
The energy (enthalpy) difference between the reactants and the transition state.

Question 3

Aldehyde

Answer 3

An organic compound with the general formula RCHO

Question 4

Alkaline earth metals

Answer 4

Group 2

Question 5

Alkane

Answer 5

Hydrocarbon with C-C and C-H single bonds only

Question 6

Allotropes

Answer 6

Pure elements which can exist in different physical forms in which their atoms are arranged differently. E.g. Diamond, graphite and buckminsterfullerene

Question 7

Atom economy

Answer 7

Describes the efficiency of a chemical reaction by comparing the total number of atoms in the product with the total number of atoms in the starting materials

Question 8

Atomic orbital

Answer 8

Space around the atomic nucleus where there is a high probability of finding an electron

Question 9

Avogadro constant

Answer 9

Number of particles in one mole of a substance

6.023 x 10(23)

Question 10

Bond dissociation enthalpy

Answer 10

The enthalpy change required to break a covalent bond with all species in the gaseous state

Question 11

Calorimeter

Answer 11

Instrument for measuring the heat changes that accompany chemical reactions

Question 12

Catalytic cracking

Answer 12

The breaking, either the aid of a catalyst, of long-chain alkane molecules (from crude oil) into short chain hydrocarbons.

Question 13

Catalyst

Answer 13

Substance that alters the rate of chemical reaction without being used up.
It provides an alternate pathway for the reaction that uses a lower activation energy.

Question 14

Carbocation

Answer 14

An organic ion in which one carbon has a positive charge

Question 15

Carbon-neutral

Answer 15

A process in which as much CO2 is absorbed as is released

Question 16

Chemical feedstock

Answer 16

The starting materials in a industrial chemical process

Question 17

Co-ordinate bonding

Answer 17

Covalent bonding in which both the electrons in the bond come from one atom

Question 18

Covalent bond

Answer 18

2 electron pairs shared between two atoms in a bond

Question 19

Displacement reaction

Answer 19

Reaction in which an atom replaces another in a compound

Question 20

Disproportionation

Answer 20

Redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same element decreases

Question 21

Electron pair repulsion theory

Answer 21

Explains the shapes of simple molecules by assuming pairs of electrons around a central atom repel each other and take up positions as far away as possible from each other in space

Question 22

Electrophile

Answer 22

Electron-deficient atom,ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant

Question 23

Enthalpy change

Answer 23

Measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure

Question 24

Finger print region

Answer 24

Area of an infra red spectrum below about 1500cm-1

Caused by complex vibrations of the whole molecule and is characteristic of a particular molecule

Question 25

Ionisation energy

Answer 25

Energy required to remove a mole of electrons from a mole of isolated gaseous atoms or ions

Question 26

Maxwell Boltzmann distribution

Answer 26

Distribution of energies of molecules in a gas or liquid

Question 27

Oxidising agent

Answer 27

Reagent that accepts electrons

Question 28

Reducing agent

Answer 28

Electron donor

Question 29

Polar

Answer 29

Molecule with a non symmetrically disoriented charge

Question 30

Positive inductive effect

Answer 30

Describes tendency of some atoms or groups of atoms to release electrons via a covalent bond

Question 31

Specific heat capacity

Answer 31

Amount of heat need to raise the temperature of 1g of a substance by 1K

Question 32

Standard molar enthalpy change of combustion

Answer 32

Enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in their standard states

Question 33

Standard molar enthalpy change of formation

Answer 33

Enthalpy change when 1 mole of a substance is formed from its elements with all reactants and products in their standard states

Question 34

Hess’s law

Answer 34

The enthalpy change for a chemical reaction is independent of the route taken

Question 35

Me Châtelier’s principle

Answer 35

If a system at equilibrium is disturbed, the equilibrium moves in the direction that reduces the disturbance

Question 36

Salt

Answer 36

Any chemical compound formed from the reaction between an acid an a base, with all or part of the hydrogen of the acid replaced by a metal or cation

Question 37

Macromolecular

Answer 37

Giant molecule with covalent bonding