chemistry definitions

Question 1

molar mass

Answer 1

mass in grams of one mole of that substance

Question 2

molar concentration

Answer 2

the amount of solute per unit volume of solution

Question 3

electronegativity

Answer 3

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

Question 4

heat of a reaction (h)

Answer 4

the net change of chemical potential energy of the system

Question 5

exothermic reaction

Answer 5

reactions which transform chemical potential energy into thermal energy

Question 6

endothermic reaction

Answer 6

reactions which transforms thermal energy into chemical potential

Question 7

activation energy

Answer 7

the minimum energy required to start a chemical reaction

Question 8

activated complex

Answer 8

a high energy, unstable transitions state between reactants and products

Question 9

rate of reaction

Answer 9

as the change in amount or concentration per unit time of either a reactant or product

Question 10

catalyst

Answer 10

a substance that increases the rate of reaction but remains unchanged at the end of the reaction

Question 11

what is the collision theory

Answer 11

a model that explains that a reaction will only proceed when reactant particles collide effectively

Question 12

what makes an effective collision

Answer 12

correct orientation, sufficient kinetic energy (greater or equal to activation energy)

Question 13

what is a closed system

Answer 13

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

Question 14

what is a open system

Answer 14

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

Question 15

state le chateliers principle

Answer 15

when an external stress (change in pressure, temperature or concentration) is applieed to a system in dynamic chemical equilbrium , the equalbrium point will change in such a way as to counteract the stress

Question 16

acid

Answer 16

proton donor

Question 17

base

Answer 17

proton acceptor

Question 18

define ionisation

Answer 18

the reaction of a molecular substance with water to produce ions

Question 19

what is a strong acid

Answer 19

an acid that ionises almost completely in an aqueous solution

Question 20

weak acid

Answer 20

an acid that only ionises partically in an aqueous solution

Question 21

dissociation

Answer 21

the splitting of an ionic compound in to its ions

Question 22

what is a strong base

Answer 22

a base that dissociates almost completely in an aqueous solution

Question 23

what is an amphoteric

Answer 23

a substance that can act as either an acid or a base

Question 24

weak acid

Answer 24

a base that only ionises partially in an aqueous solution

Question 25

salt

Answer 25

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

Question 26

hydrolysis of a salt

Answer 26

a reaction of an ion (from a salt) with water

Question 27

neutralisation

Answer 27

a chemical reaction in which an acid and a base react so neither is in excess

Question 28

standard solution

Answer 28

a solution of known concentration

Question 29

redox reaction

Answer 29

a reaction involving the transfer of electrons

Question 30

oxidation

Answer 30

a loss of electrons

Question 31

reduction

Answer 31

gain of electrons

Question 32

oxidising agent

Answer 32

a substance that accepts electrons

Question 33

reducing agent

Answer 33

a substance that donates electrons

Question 34

anode

Answer 34

the electrode where oxidation takes place

Question 35

cathode

Answer 35

electrode where reduction takes place

Question 36

electrolyte

Answer 36

a substance that can conduct electricity due to the presence of free (mobile) ions where molten or dissolved in solution

Question 37

hydrocarbon

Answer 37

a compound containing only carbon and hydrogen bonds

Question 38

saturated compound

Answer 38

a compound in which all of the bonds between carbon atoms are single bonds

Question 39

unsaturated compound

Answer 39

a compound in which there is at least on double/or triple bond between carbon atoms

Question 40

functional group

Answer 40

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

Question 41

homologous series

Answer 41

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

Question 42

structural isomers

Answer 42

compounds having the same molecular formula but different structural formulae