Group 14

Question 1

Describe group 14 halides

Answer 1

1. All halides of the form EX4 are known except PbI4
2. CF4, CCl4 are inert
3. Sn, Pb: EX2 is more stable than EX4 (especially Pb)

Question 2

How are Si halides hydrolysed

Answer 2

1. Readily hydrolysed by H2O

2. SiCl4 + 2H2O –> SiO2 + 4HCl

Question 3

Why is Si more prone to attack by nucleophiles than C

Answer 3

1. It is bigger than C

Question 4

What is SnCl2 used as

Answer 4

1. A reducing agent

2. Oxidised to SnCl(IV)

Question 5

Describe SnCl4

Answer 5

1. Liquid, freezing at -33 degrees

2. Indicates that it is molecular rather than ionic

Question 6

Why is Pb(II) more stable than Pb(IV)

Answer 6

1. Inert pair effect

Question 7

Compare reaction of Sn/Pb to groups 1,2,13 e.g. Al

Answer 7

1. Less vigorously
2. Al reacts vigorouly with HCl dilute and H2SO4 dilute
3. Sn reacts slowly with dilute but more rapidly with conc. acids

Question 8

What are the difference in products of Sn and Pb reactions with acids

Answer 8

1. Pb products are insoluble

2. Adhere to metal and stop the reaction continuing

Question 9

Describe carbon monoxide

Answer 9

1. Formed when C burns in a limited air supply

2. Binds to Fe in haemoglobin preventing transport of O2 around the body

Question 10

Describe solubility of CO2

Answer 10

1. Water soluble
2. CO2 + H2O H2CO3 H3O+ + HCO3-
3. H3O+ + H2O H3O+ + CO32-

Question 11

What is the difference between CO2 and SiO2

Answer 11

1. SiO2 forms covalent networks

2. Due to single and double bond strengths

Question 12

How can you calculate if a network or gas is more favourable for CO2

Answer 12

1. Network 4*single C-O bonds
2. CO2 gas C=O*2
3. Find difference in enthalpies
   4 CO2 (Network)–> CO2 (gas)
4. Uses DH rather than DG but can be used to show a general trend rather than include DS

Question 13

How is sodiu silicate formed

Answer 13

1. SiO2 + Na2CO3 –> Na4SiO4 + 2CO2

Question 14

Describe sodium silicate

Answer 14

1. Form extended structures, tetrahedral at Si
2. Conductors (Microchips)
3. Good thermal properties (Ceramics)

Question 15

What are silicones

Answer 15

1. Si-O containing polymers
2. Properties depend on the nature of the organic substituent
3. Used as lubricant and medical implants

Question 16

What can PbO2 be used as

Answer 16

1. A strong oxidising agent: Pb(IV) is easily reduced to Pb (II) ie PbO

Question 17

Describe the catenation and allotropy of carbon

Answer 17

1. Diamond- 3D network, sp3 bonds, strong bonds, insulator
2. Graphite- stacked hexagonal rings, sp2 bonds, Pi bonding perpendicular to sheets, conductor
3. Fullerenes- molecular carbon cages

Question 18

Describe the catenation and allotropy of silicon and Ge

Answer 18

1. Metalloids
2. Semiconductors
3. diamond structures

Question 19

Describe the catenation and allotropy of Sn

Answer 19

1. Diamond structure- covalent, grey

2. Interactions with more than 4 nearest neighbours, more metallic, white

Question 20

Describe the catenation and allotropy of Pb

Answer 20

1. Fully metallic in nature