Definitions

Question 1

Define isotope

Answer 1

Atoms of an element with the same number of protons but different numbers of neutrons

Question 2

Define relative atomic mass

Answer 2

Average mass of an atom of an element compared to one-twelfth of the mass of an atom of carbon-12

Question 3

Define relative molecular mass

Answer 3

The average mass of a molecule relative to one-twelfth of the mass of an atom of carbon-12

Question 4

Define relative formula mass

Answer 4

Total of relative atomic masses in a compound

Question 5

Define isotopic abundance

Answer 5

Relative proportions of stable isotopes of each element

Question 6

Define first ionisation energy

Answer 6

The energy needed to remove an electron from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 7

Avagadros constant and formula

Answer 7

6.022x10^23 = L

Number of particles = moles x L

Question 8

Ideal gas equation

Answer 8

pV = nRT

Question 9

Define empirical formula and molecular formula

Answer 9

Empirical formula is the simplest whole number ratio of atoms of each element in a compound.

Molecular formula is the actual number of atoms of each element in a compound

Question 10

Define electronegativity

Answer 10

the power of an atom to attract the pair of electrons in a covalent bond

Question 11

Define co-ordinate bond

Answer 11

bond containing a shared pair of electrons with both electrons supplied by one atom.

Question 12

Define enthalpy change

Answer 12

change in heat energy under constant pressure

Question 13

define standard enthalpy of combustion (∆cHƟ)

Answer 13

the enthalpy change when one mole of substance burns completely in oxygen under standard conditions in standard states

Question 14

define standard enthalpy of formation (∆fHƟ)

Answer 14

the enthalpy change when one mole of substance is formed from its constituent elements in standard states under standard conditions

Question 15

State Hess’ Law

Answer 15

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

Question 16

Define mean bond enthalpy

Answer 16

The energy required to break a covalent bond in a molecule averaged over a range of compounds

Question 17

Define activation energy

Answer 17

Minimum amount of energy required to start a reaction

Question 18

Define rate of reaction

Answer 18

The change in concentration of a substance in a given time

Question 19

Define catalyst

Answer 19

substance that increases the rate of a chemical reaction without being changed in chemical composition or amount

work by providing an alternative reaction route of lower activation energy

Question 20

State Le Chatelier’s principle

Answer 20

If a change is made to a system in dynamic equilibrium, the equilibrium position shifts to counteract this change

Question 21

Define oxidation

Answer 21

Loss of electrons

Question 22

Define reduction

Answer 22

Gain of electrons

Question 23

Define oxidising agent

Answer 23

Electron acceptors

Question 24

Define reducing agent

Answer 24

Electron donors

Question 25

Define free radical

Answer 25

Highly reactive species with an unpaired electron

Question 26

Define structural isomerism

Answer 26

Compounds with the same molecular formula but different structural formula

Question 27

Define stereoisomerism

Answer 27

Compounds with the same structural formula but different arrangement of atoms in space

Question 28

Define hydrocarbon

Answer 28

Compound that only contains carbon and hydrogen atoms

Question 29

Define nucleophile

Answer 29

electron pair donor

Question 30

Define electrophile

Answer 30

electron pair acceptor

Question 31

Explain positive inductive effect

Answer 31

Electrons move away from a group towards the apecies which is more electronegative

Question 32

Define biofuel

Answer 32

Fuels with a plant-based origin