Chemistry Definitions

Question 1

Mole

Answer 1

The amount of substances which contain Avogadro’s number of particles

Question 2

Molar mass

Answer 2

The mass in grams of one mole of that substance

Question 3

Molar volume

Answer 3

The volume occupied by 1 mole of gas at STP. 1 mole of gas occupied 22,4dm3 at 0°C (273k) and 1 atmosphere (101,3kPa)

Question 4

Solution

Answer 4

A homogenous mixture of solute and solvent

Question 5

Solute

Answer 5

The substance that is dissolved in the solution

Question 6

Solvent

Answer 6

The substance in which another substance is dissolved forming a solution

Question 7

Yield

Answer 7

A measure of the extent of a reaction, generally measured by comparing the amount of product against the amount of product possible

Question 8

Intramolecular bond

Answer 8

A bond between atoms within molecules

Question 9

Covalent bond

Answer 9

A sharing of at least one pair of electrons by two non metal atoms

Question 10

Non-polar covalent bond

Answer 10

An equal sharing of electrons

Question 11

Polar covalent bond

Answer 11

Unequal sharing of electrons leading to a dipole forming (as a result of electronegativity difference)

Question 12

Electronegativity

Answer 12

A measure of tendency of an atom to attract a bonding pair of electrons

Question 13

Ionic bond

Answer 13

A transfer of electrons and subsequent electrostatic attraction

Question 14

Metallic bonding

Answer 14

Being between a positive kernel and a sea of delocalised electrons

Question 15

Intermolecular force

Answer 15

A force between molecules, ions, or atoms of noble gases

Question 16

Heat of a reaction

Answer 16

The net change of chemical potential energy into thermal energy

Question 17

Endothermic reactions

Answer 17

Reactions which transform thermal energy Into chemical potential energy 

Question 18

Activation energy

Answer 18

The energy required to form the activated complex

Question 19

Activated complex

Answer 19

A high energy, unstable, temporary transition state between the reactants and the products

Question 20

Reaction rate

Answer 20

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

Question 21

Catalyst

Answer 21

A substance that increases the rate of the reaction but remains and changed at the end of the reaction 

Question 22

Affective (successful) collision

Answer 22

A collision in which the colliding reactant particles have the correct orientation and the sufficient energy (kinetic energy equal to or greater than the activation energy)

Question 23

Closed system

Answer 23

A system in which mass is conserved inside the system but energy can enter or leave the system freely

Question 24

Open system

Answer 24

A system in which both energy and matter can be exchanged between the system and its surroundings

Question 25

Reversible reaction

Answer 25

A reaction in which products can be converted back into reactants 

Question 26

Dynamic chemical equilibrium

Answer 26

Irreversible reaction in which the forward and reverse reactions are taking place at the same rate, and hence the concentrations of reactants and products are constant

Question 27

Le Chatelier’s principle

Answer 27

When an external stress (change in pressure, temperature or concentration) is applied to a system and dynamic chemical equilibrium, the equilibria point will change in such a way as to counteract the stress

Question 28

Equilibrium constant Kc

Answer 28

Temperature is the only factor which influences the valley of the equilibrium constant

Question 29

Acid

Answer 29

A proton donor

Question 30

Base

Answer 30

A proton acceptor 

Question 31

Ionisation

Answer 31

The reaction of a molecular substance with water to produce ions 

Question 32

Strong acid

Answer 32

In acid that ionises completely in an aqueous solution

Question 33

Weak acid

Answer 33

An acid that only ionises partially in an aqueous solution

Question 34

Dissociation

Answer 34

The splitting of an ionic compound into its ions

Question 35

Strong base

Answer 35

A bass that dissociates completely in an aqueous solution

Question 36

Weak base

Answer 36

A bass that only dissociates/ionises partially in an aqueous solution

Question 37

Amphoteric or amphiprotic substance 

Answer 37

A substance that can act as either an acid or base

Question 38

Salt

Answer 38

A substance in which the hydrogen of an acid has been replaced by a cation

Question 39

Hydrolysis of a salt

Answer 39

Reaction of an iron (from a salt) with water

Question 40

Neutralisation (or the equivalence point)

Answer 40

The point where an acid and base have reacted so neither is in excess 

Question 41

Standard solution

Answer 41

A solution of known concentration

Question 42

Redox reaction

Answer 42

A reaction involving the transfer of electrons

Question 43

Oxidation

Answer 43

The loss of electrons

Question 44

Reduction

Answer 44

The gain of electrons

Question 45

Oxidising agent

Answer 45

a substance that accepts electrons

Question 46

Reducing agent

Answer 46

A substance that donates electrons

Question 47

Anode

Answer 47

The electrode where oxidation takes place

Question 48

Cathode

Answer 48

The electrode where reduction takes place

Question 49

Electrolyte

Answer 49

A substance that can conduct electricity by forming free irons when molten or dissolved in a solution

Question 50

Hydrocarbon

Answer 50

A compound containing only carbon and hydrogen atoms

Question 51

Saturated compound

Answer 51

A compound in which all the bonds between carbon atoms are single bonds

Question 52

Unsaturated compound

Answer 52

A compound in which there is at least one double and/or triple bond between carbon atoms

Question 53

Functional group

Answer 53

An atom or a group of atoms that form the centre of chemical activity in the molecule

Question 54

Homologous series

Answer 54

A series of similar compounds which have the same functional group and the same general formula in which each member differs from the previous one by a single CH2 unit

Question 55

Structural isomers

Answer 55

Compounds having the same molecular formula but different structural formulae

Question 56

Cracking

Answer 56

The breaking up (cracking) of a large hydrocarbon molecules into smaller and more useful molecules (specifically a smaller hydrocarbon and one or more small alkenes)

Question 57

Concentration

Answer 57

The amount of solute per unit volume of solution

Question 58

Intramolecular bonds

Question 59

Dipole dipole

Question 60

London forces

Question 61

Hydrogen bonds

Answer 61

A small atom High electronegativity With at least one lone pair of electrons

Question 62

Strength of london forces

Answer 62

Influenced by size of the temporary dipoles Which is influenced by: No. Of electrons Longbranched chain vs branched chain

Question 63

Melting point of giant structures

Answer 63

Diamond Graphite Silicon dioxide Melting and boiling points are high due to the large amount of energy needed to break the many strong covalent bonds

Question 64

Melting or boiling points in giant ionic structures

Answer 64

The melting or boiling points are determined by electrostatic forces of attraction between the cations and the anions in the lattice structure