Giant Structure

Question 1

Name 3 methods of proving ion existence

Answer 1

Electrolysis
Ion migration
X-ray crystallography

Question 2

How does electrolysis prove ion existence

Answer 2

aq/l
Conduct electricity
Free delocalised electrons to carry charge

Question 3

How does ion migration prove ion existence

Answer 3

aq coloured ions
Copper chromate solution soaked paper
Crocodile clips, DC power supply
Blue copper cations, yellow chromate anions

Question 4

How does X-ray crystallography prove ion existence

Answer 4

Diffract through slag crystal
Electron density map
Contours link equal charge regions
Separate ionic solid entities

Question 5

Lattice energy

Answer 5

Energy change to make 1 mole of a solid ionic crystal from its gaseous ions
Exo

Question 6

Standard enthalpy change of formation

Answer 6

Energy change to make 1 mole of a compound from it’s elements in their standard state under standard conditions

Question 7

Standard enthalpy change of atomisation

Answer 7

Energy change to make 1 mole of gaseous atoms from it’s elements in their standard state under standard conditions
Endo

Question 8

Ionisation energy

Answer 8

Energy to remove 1 electron from each atom/ion in 1 mole of gaseous atoms/ions
Endo

Question 9

Electron affinity

Answer 9

Energy change to add 1 electron to each atom/ion in 1 mole of gaseous atoms/ions

Question 10

Describe the energetics pattern of electron affinity

Answer 10

From neutral = exo
From negative = endo
Negative charge of ion and negative charge of electron repel each other, energy must be absorbed to overcome the ESR

Question 11

Describe the 3 general layers of a borne haber cycle

Answer 11

Natural elements
Gaseous ions
Solid lattice

Question 12

Describe the differences (4) between a BHC of NaCl and MgCl2

Answer 12

Higher IEs
Higher No.IEs
Higher lattice enthalpy
Double Cl values

Question 13

Name 3 factors that effect LE

Answer 13

Charge of ions
Size of ions
No. Ions

Question 14

BHC exam technique terminology

Answer 14

X larger/smaller
More Endo/exo
State what is

Question 15

How does charge effect LE

Answer 15

Higher charge
Higher ESA between ions
Higher ETO
More exo LE

Question 16

How does ion size effect LE

Answer 16

Larger size
Ions further away
Less ESA
Less exo LE

Question 17

Exam technique factors effecting LE

Answer 17

State what’s the same and what’s different

Question 18

What’s influences theoretical LE

Answer 18

Ion attraction/repulsion

Question 19

How do you calculate the theoretical LE

Answer 19

Charges + distance between ions —> sum of forces

Question 20

Describe 3 reasons why theoretical LE is calculated

Answer 20

BH experimental data doesn’t exist
Use in BH to find (usually) less exo enthalpy of formation for unexpected compounds
Compare T + E, find validity, more than 10% difference = insufficient model, usually covalent bonding present

Question 21

Describe metallic bonding structure

Answer 21

Close packed giant lattice of positive ions and a sea of delocalised electrons
Held together by ESA between positive ions and negative electrons

Question 22

Name 3 properties of metallically bonded structures

Answer 22

High mp/bp
Malleable
Electrical conductor

Question 23

Why are metallic structures malleable

Answer 23

Same layers
Movement doesn’t change bonding

Question 24

Why are metallic structures electric conductors

Answer 24

Delocalised electrons from ions carry charge through substance

Question 25

Why do metallic structures have high mp/bp

Answer 25

Giant structures Many strong bonds More ETO

Question 26

Enthalpy change of solution

Answer 26

Enthalpy change for 1 mole of a substance to dissolve in water to become a solution of infinite dilution

Question 27

Enthalpy change of hydration

Answer 27

Enthalpy change for 1 mole of gaseous ions to dissolve in water to become a solution of infinite dilution

Question 28

Describe the appearance of a hydrated ion

Answer 28

Ion surrounded by opposite charge atoms of water molecules

Question 29

Describe what happens when an ionic solid dissolves in water

Answer 29

Crystal lattice broken (endo) Water H bonds broken (endo) H point at cation O point at anion ESA (exo) Hydration

Question 30

Describe a hydration cycle

Answer 30

Gaseous ions at top Aqueous ions in middle Solid lattice at bottom

Question 31

Why is finding the enthalpy of solution from a hydration cycle unreliable (4)

Answer 31

- Small difference between 2 much larger values that can’t be directly found and are effected by charge and size factors - Small % uncertainty in LE of hydration enthalpy can —> large solution enthalpy % uncertainty - Solution enthalpy isn’t only solubility factor, endo solution enthalpy won’t dissolve well, large LE - Soluble compounds can form saturated solution

Question 32

Why does poor E + T LE agreement occur

Answer 32

Polarisation of anion by cation Cation distorts electron cloud on anion Pulls towards shared region Nearly electron sharing Some covalent character Stronger bonding ELE more exo than TLE suggests

Question 33

Anion and cation properties in polarisation

Answer 33

Cation, polarising power Anion, polarisability

Question 34

What factors INCREASE polarising power of cation

Answer 34

Increase cation charge Decrease cation size Higher positive charge density = more effective distortion

Question 35

What factors INCREASE polarisability of anion

Answer 35

Increase charge Increase size Larger ion = less grip on outer electrons = easier to distort

Question 36

Name 4 levels on bonding spectrum

Answer 36

Pure covalent Polar covalent (unequal shared electrons) Polar ionic (distorted ions) Pure ionic

Question 37

Name 3 allotropes of carbon

Answer 37

Diamond Graphite Graphene

Question 38

Graphite 4 properties 2 uses

Answer 38

- Conductor, delocalised electrons between layers - Sheet formation - Each C bonded to 3 others - Soft, layers can slide Uses, electrics, pencils

Question 39

Diamond 7 properties

Answer 39

- All Cs cov bonded to 4 others - Tetrahedral structure - High mp, lots ETO, many bonds - Hard, strong bonds, lattice arrangement - Thermal conductor, vibrations travel through stiff lattice - Insoluble, more attracted to neighbouring atoms that solvent molecules, no ions - Not electrical conductor, no free electrons/ions

Question 40

Graphene 6 properties

Answer 40

One sheet of graphite, joined by 2 hexagons 2D, one atom thick Conductor, delocalised electrons Strong Transparent Light