P-Block

Question 1

What is the inert pair effect?

Answer 1

In group 4 the inert pair effect means lighter elements e.g carbon are more stable in a 4+ oxidation state while heavier elements e.g lead are more stable ina 2+ oxidation state. This is why PbO and CO2 are more common than PbO2 and CO

Question 2

Why is CO a strong reducing agent?

Answer 2

Since the carbon is in the 2+ state and aims to reach the 4+ state it loses electrons easily
Fe2O3 + 3CO -> 2Fe + 3CO2

Question 3

Why is PbO2 a strong oxidising agent?

Answer 3

The Pb is in the 4+ states and aims to reach the 2+ state so it gains electrons easily
PbO2 + 4HCl -> PbCl2 + Cl2 + 2H2O

Question 4

Explain why the max covalency for period 2 is 4

Answer 4

No other orbitals are available for electrons

Question 5

Explain why the max covalency for periods >2 is 4,5 or 6

Answer 5

The d-orbital is available for electrons to move into eg in phosphorous

Question 6

What is electron deficiency?

Answer 6

Lack of complete valence shell

Question 7

How can AlCl3 dimerise? (eqn)

Answer 7

2AlCl3 -> Al2Cl6

Question 8

What is the difference in shape of the two types of aluminium chloride?

Answer 8

AlCl3 - Trigonal planar

Al2Cl6 - tetrahedral

Question 9

How does ammonia and boron tetrafluoride form a donor acceptor pair?

Answer 9

The nitrogen has a lone pair of electrons to fill the space in the borons valence shell forming a coordinate bond

Question 10

What is an amphoteric compound?

Answer 10

A compound that can react with acids and bases

Question 11

How can lead and hydroxide be amphoteric?

Answer 11

Pb2+ (aq) + 2OH- (aq) -> Pb(OH)2(s)

This can be reversed with the addition of an acid

Question 12

What is meant by isoelectronic?

Answer 12

Molecules that have the same electron configuration

Question 13

Why can’t H-BN conduct heat like graphite?

Answer 13

Both molecules contain a spare p-orbital however H-BN spare p-orbital doesn’t have any free electrons to carry charge while graphite does

Question 14

How is C-BN similar to diamond?

Answer 14

Both have lattice structures with strong electrostatic forces between them hence why they are very solid

Question 15

What is C-BN used for?

Answer 15

C-BN is used for coating on cutting equipment and on bullet coatings due to its strength

Question 16

What is H-BN used for?

Answer 16

H-BN is used as a lubricant due to its weak layers

Question 17

How is H-BN similar to graphite?

Answer 17

Both have layers of hexagonal molecules with weak VDW forces between them

Question 18

Describe CCl4 and its reaction with water

Answer 18

• Tetrahedral structure
• colourless liquid
• immiscible with water so it doesn’t react

Question 19

Describe SiCl4 and its reaction with water

Answer 19

• Tetrahedral
• colourless liquid
• white fumes
• reacts vigorously to form SiO2

Question 20

Describe PbCl2 and its reaction with water

Answer 20

• White insoluble solid

- Dissolves to produce tetrachlorolead ion and HCl

Question 21

What is a disproportionation reaction?

Answer 21

A reaction where an element is both reduced and oxidised at the same time

Question 22

Reaction of chlorine with Cold dilute OH- and its effect on oxidation number

Answer 22

Cl2 + 2OH- -> Cl- + ClO- + H2O

(-1) (+1)

Question 23

Reaction of chlorine with warm conc. OH- and its effect on oxidation number

Answer 23

Cl2 + 6OH- -> 5Cl- + ClO3- + 3H2O

(-1). (+5)

Question 24

Describe how NaCl reacts with water

Answer 24

misty white fumes (HCl)

Question 25

Describe how NaBr reacts with H2SO4

Answer 25

misty white fumes (HBr)
brown fumes (Br2)
choking gas (SO2)

Question 26

Describe how NaI reacts with water

Answer 26

misty white fumes (HI)
purple fumes (I2)
choking gas (SO2)
Rotten egg smell (S)