Izod L7-9

Question 1

Describe germanium chemistry

Answer 1

Ge very similar to Si: +4 oxidation states dominate but +2 accessible. Ge-X bonds stronger than expected due to X->Ge hyperconjugation, but overlap of X l.p with Ge-X σ* poorer therefor weaker σ bond and hyperconjugation.

Question 2

What oxidation state does Sn adopt

Answer 2

Sn both +4 and +2 oxidation states dominate accessible

Question 3

What oxidation state does Pb adopt

Answer 3

Pb +2 oxidation states dominates

Question 4

Describe SnX2 compounds

Answer 4

SnX2 compounds are Lewis acids as they are electron deficient but are also also Lewis bases because they have a lone pair. For example SnCl2 polymerises with stereochemically active lone pair.

Question 5

Define catenation

Answer 5

Catenation is the ability of an element to form bonds with itself, creating chains or rings of atoms of the same element

Question 6

Describe catenation for Si and Ge

Answer 6

Si and Ge forms long chains

Question 7

Describe catenation for Sn

Answer 7

For Sn mostly cycles

Question 8

Describe E=E for group 14

Answer 8

C=C sigma and pi orverlap very good. For Ge-Pb valence orbitals are large/diffuse therefore very poor pi overlap so E=E is quite rate.

Question 9

Describe electron configuration for group 15

Answer 9

Ground state electron configuration ns2np3

Question 10

Describe the oxidation states for group 15 elements

Answer 10

+3 oxidation state common for all elements
+5 for N,P,As,Sb

Question 11

Describe ammonia

Answer 11

Ammonia produces by harber-Bosch process
N2 + 3H2 -> 2NH3
Industrially used in fertiliser and explosives. NH3 has high b.p due to extensive H bonding (N-H - - - N) used as a solvent

Question 12

Describe hydrazine

Answer 12

N2H4 produced by oxidation of ammonia. Good reducing agent readily oxidised by O2
N2H4 + O2 -> N2 + 2H2O
Used as rocket propellant

Question 13

Describe nitrogen monoxide

Answer 13

NO colourless gas, odd electron radical species. Unpaired electron in delocalised pi* orbital therefore not stable

Question 14

Describe nitrogen dioxide

Answer 14

Radical (singly occupied molecular orbital localised on N atom) therefore reactive.

Question 15

What is the equilibrium of NO2 with and what does it depend on

Answer 15

2NO2 in equilibrium with N2O4 and position of equilibrium controlled by temperature and pressure.

Question 16

Describe nitric acid and the reaction if is synthesised by

Answer 16

Nitric acid is a very strong acid and synthesised by catalysed oxidation of NH3
NH3 + 2O2 -> HNO3 + H2O
Nitric acid is also a strong oxidising agent

Question 17

Describe how HNO3 oxidised Cu

Answer 17

4HNO3 + Cu —> Cu(NO3)2 + 2NO2 + 2H2O

Question 18

Describe nitrogen halides

Answer 18

NF3 - stable gas very unreactive
NCl3 - volatile liquid explosive
NBr3/NI3 - too reactive/ e plosive for isolation

Question 19

Describe what structure phosphorus prefers

Answer 19

P prefers pyramidal structure eg P4

Question 20

Why is N2 more stable than P2

Answer 20

For N, N triple bond N much stronger than 3xN-N for P, P triple bond P much weaker than 3xP-P. P-P favoured

Question 21

Describe phosphorus hydrides

Answer 21

PH3 - toxic gas
P2H4 - not common

Question 22

What are phosphorus main oxides

Answer 22

Two main oxides
- P4O6
- P4O10

Question 23

What are the phosphorus oxoacids

Answer 23

Phosphoric acid
Phosphonic acid
Phosphinic acid

Question 24

Describe the phosphorus trihalides

Answer 24

All trihalides known, very useful for synthesis of phosphines, insecticides, plasticisers, flame retardants.
Oxidise/hydrolyse readily

Question 25

Write the oxidation and hydrolysis of PCl3

Answer 25

PCl3 + 1/2O2 -> Cl3P=O PCl3 + 3H2O -> H3PO4 + 3HCl

Question 26

Describe the bonding in PF5

Answer 26

Forms 5 bonding but only has 4 valence orbitals (3s and 3x3p). P atom hypervalent. Bonding explained using multi-centre bonding scheme.

Question 27

Describe the hydrides of As, Sb, Bi

Answer 27

Very toxic, increasingly unstable down group. Poor E-H sigma overlap.

Question 28

Describe the halides of As, Sb, Bi

Answer 28

All trihalides know/stable buy penrahalides confirmed to EF5 not know EBr5 and EI5

Question 29

Describe the oxides of As, Sb, Bi

Answer 29

All E2O6 known Only As2O5 known due to inert lone pair effect

Question 30

Describe the ground state electron configuration of group 16

Answer 30

Ground state electron configuration ns2np4

Question 31

What are the common oxidation states for group 16

Answer 31

2,4,6

Question 32

What are the hydrides for oxygen

Answer 32

H2O, H2O2

Question 33

Describe H2O2 and its reactions acting as an oxidising agent, reducing agent and how it can disproportionate

Answer 33

Can act as an oxidising agent H2O2 + 2H+ + 2e- -> 2H2O And a reducing agent H2O2 -> O2 + 2H+ +2e- Can disproportionate 2H2O2 —> 2H2O + O2

Question 34

Describe the oxygen halides

Answer 34

Only fluorides known OF2 - colourless poisonous gas O2F2 - yellow liquid below -100 degrees, structure similar to H2O2

Question 35

Describe the sulphur hydrides

Answer 35

Only H2S important. H2S very toxic

Question 36

List the sulfur oxides and describe them

Answer 36

Most stable oxides are SO2 and SO3 SO2 - toxic gas at room temperature by product of burning fossil fuels SO3 - toxic gas at room temperature

Question 37

List the sulfur fluorides

Answer 37

S2F2 SF2 S2F4 SF4 S2F10 SF6

Question 38

List the know sulfur chlorides

Answer 38

SCl2, S2Cl2

Question 39

Describe S-N compounds

Answer 39

S4N4 Kinetically stable but thermodynamically unstable S4N4 —> 1/2 S8 + N2