Definitions

Question 1

Define the relative isotopic mass (2 marks)

Answer 1

Mass of an atom of that isotope
Relative to 1/12th mass of a C-12 atom

Question 2

Define relative atomic mass (2 marks)

Answer 2

Mean mass of an atom
Relative to 1/12th mass of a C-12 atom

Question 3

What is a covalent bond (2 marks)

Answer 3

electrostatic attraction between 2 nuclei
Between bonding pairs of electrons

Question 4

Define periodicity in terms of atomic radius in P2 and P3 (3 marks)

Answer 4

• pattern of repeating physical and chemical properties with increasing atomic number
• atomic radii decreases across the period
• trends repeated in Period 3

Question 5

Define ionic bonds (2 marks)

Answer 5

(Strong) Electrostatic attraction
Between oppositely charged ions

Question 6

Define ionic bonds (2 marks)

Answer 6

(Strong) Electrostatic attraction
Between oppositely charged ions

Question 7

In the mass spectrum of silicon, there is also a small peak at m/z = 14. Deduce the formula of this particle.

Answer 7

28 Si2+

Question 8

What is the definition of electronegativity? (2 marks)

Answer 8

• Measure of an atom’s ability to attract a pair of e-s
• in a covalent bond

Question 9

Define an acid.

Answer 9

A proton donor

Question 10

What is an activation energy?

Answer 10

Minimum energy required for collision to be successful in a reaction

Question 11

What is a mole?

Answer 11

Amount of substance that contains the same number of particles as the number of carbon atoms in exactly 12g of C12 isotope

Question 12

Define autocatalysis

Answer 12

When a product of a reaction acts as a catalyst

Question 13

What does Avogadro’s constant stand for

Answer 13

The number of 12C atoms in exactly 12g of 12C

Question 14

Define a base

Answer 14

Proton acceptor

Question 15

Define chiral molecules.

Answer 15

Molecules that contain a carbon atom attached to four different groups

Question 16

Define a dimer

Answer 16

Molecule consists of 2 monomers to form a stable structure

Question 17

Define electronegativity.

Answer 17

Ability for an atom to attract bonding pairs of electrons-s in a covalent bond

Question 18

Define an electrophile.

Answer 18

A species attracted to a region of high electron density
(Lone pair acceptor)

Question 19

Define enthalpy change.

Answer 19

Heat energy change at constant pressure of 100kPa

Question 20

Define entropy

Answer 20

Measure of disorder

Question 21

Define first electron affinity.

Answer 21

Enthalpy released when 1 mole of electrons is gained by 1 mole of gaseous atoms forming 1 mole of 1- gaseous ions
(Exothermic as bond forming)

Question 22

Define first ionisation energy.

Answer 22

Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of 1+ ions under standard conditions

Question 23

Define free radical

Answer 23

An atom having 1 unpaired electron

Question 24

Define half equivalence point

Answer 24

The point which half the acid has been neutralised by the base or vice versa

Question 25

Define half life

Answer 25

Time taken for the concentration of a reactant to decrease by half

Question 26

Define Hess’s law

Answer 26

Enthalpy change for a reaction is independent of the route taken

Question 27

Define heterolytic fission

Answer 27

Breaking of a covalent bond to form 2 different species

Question 28

Define homolytic fission

Answer 28

Breaking of a covalent bond to form 2 identical species Eg Cl2 -> 2 Cl•

Question 29

What are the colours of methyl orange in each condition?

Answer 29

Acid - red Neutral - orange Alkaline - yellow

Question 30

What are the colours of litmus in acidic and alkali conditions?

Answer 30

Acid - red Alkali - blue

Question 31

What are the colours of phenolphthalein in acidic and alkali conditions?

Answer 31

Acidic - colourless Neutral - colourless Alkaline - pink

Question 32

Define ionic bond. (2 marks)

Answer 32

Strong Electrostatic force of attraction Between opposite,y charged ions

Question 33

Define isomers

Answer 33

Molecules with the same molecular formula but a different structural formula

Question 34

Define isoelectric

Answer 34

Atoms, ions and molecules having the same number of electronic configuration

Question 35

Define lattice enthalpy.

Answer 35

Energy released when 1 mole of ionic lattice is formed from its constituent gaseous ions under standard conditions

Question 36

Define a ligand

Answer 36

Molecules that form dative covalent bonds/ coordinate bonds with a central (transition) metal ion

Question 37

Define London forces.

Answer 37

The random, instantaneous movement of electrons in a molecule that causes an instantaneous and uneven distribution of electron density which uses a dipole and neighbouring molecules which then attract

Question 38

Define mean bond enthalpy

Answer 38

Average enthalpy change when 1mole of covalent bond is broken from a range of compounds in the gas phase under standard conditions

Question 39

Define monoprotic acid

Answer 39

An acid that releases 1 proton in aqueous solution

Question 40

Define nucleophile

Answer 40

A species attracted to low electron density Can donate lone pair of electrons to form covalent bond with an electron deficient atom (electrophile)

Question 41

Define racemic mixture

Answer 41

A 50/50 mixture of 2 enantiomers

Question 42

Define reforming

Answer 42

Using heat and pressure to convert unbranded fractions into branched molecules

Question 43

Define standard electrode potential

Answer 43

EMF of electrochemical cell comprised of half cell combined with a standard hydrogen electrode at 1atm, 1 Moldm-3, 298K

Question 44

Define standard enthalpy change of atomisation

Answer 44

Enthalpy required to make 1 mole of gaseous atoms from an element in its standard state under standard conditions

Question 45

Define standard enthalpy change for combustion

Answer 45

Enthalpy change when 1 mole of substance is completely combusted under standard conditions

Question 46

Define Standard enthalpy change of formation

Answer 46

Enthalpy change when 1 mole of a compound is formed from its constituent elements, with all elements in their standard states, under standard conditions

Question 47

Define standard enthalpy change of hydration

Answer 47

Enthalpy released when 1 mole of gaseous ions is completely dissolved in an infinite volume of water

Question 48

Define standard enthalpy of neutralisation

Answer 48

enthalpy change when 1 mole of water is formed from an acid-base reaction under standard conditions.

Question 49

Define standard enthalpy of solution

Answer 49

enthalpy change when 1 mol of solid ionic compound completely dissolved in an infinite volume of water.

Question 50

Define transition metals

Answer 50

d-block elements that form 1 or more stable ions which have incomplete d-subshells.

Question 51

What does volatile mean.

Answer 51

Tendency of a substance to easily evaporate

Question 52

What is the definition of relative atomic mass? (2 marks)

Answer 52

- the **weighted** mean mass of all isotopes of an element - relative to 1/12 of the mass of an atom of carbon-12

Question 53

What is the meaning of an orbital. (2 marks)

Answer 53

- An area / space - that can hold 2 electrons with opposite spin

Question 54

What is the definition of lattice energy.

Answer 54

Energy change when one mole of ionic solid is FORMED FROM its GASEOUS IONS

Question 55

What is a metallic bond? (2 marks)

Answer 55

Strong electrostatic attraction Between metal ions and delocalised electrons

Question 56

what is the definition of buffer solution

Answer 56

solution that resists changes in pH when small amounts of acid or base are added