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A2 CHEM UNIT3 > 3.3 P-block > Flashcards

3.3 P-block Flashcards

1
Q

What is meant by a P-block element?

A
  • electronic configuration is where your last electron is in a p orbital
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2
Q

What happens as you descend group 4?

A
  • become more ionic
  • decrease in MP
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3
Q

Define the inert pair effect

A
  • the resistance of S electrons to be involved in bonding due to a tendency of an S2 pair of electrons in an atom to stay paired, leading to a lower oxidation state
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4
Q

What happens to the inert pair effect as you descend groups?

A
  • it gets stronger
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5
Q

Define electron deficiency

A
  • where outer shells don’t have a full octet
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6
Q

Tin and carbon are stable in oxidation state +4 whilst lead is more stable as +2. Explain the difference instabilities of these oxidation states

A
  • as you go down group 4 the inert pair effect becomes stronger
  • the S electrons are more reluctant to be involved in bonding hence +2 is more stable than +4
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7
Q

How do electron deficient compounds fulfil their octet?

A
  • form acceptor-donor compounds
  • form dimers
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8
Q

What is meant by a dimer?

A
  • when 2 of the same molecule join together using a coordinate bond
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9
Q

What is meant by an acceptor donor compound?

A

ie BF3 . NH3
- ammonia has lone pair to donate into boron to fulfil octet
- coordinately bonded

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10
Q

What enables octet expansion?

A
  • empty d and f orbitals
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11
Q

Adding a lone pair reduces the bond angle by …?

A

2.5°

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12
Q

Explain why nitrogen can only form a chloride with 8 outer shell electrons, but phosphorus can form a chloride with a different number of outer shell electrons

A
  • phosphorous can form a chloride with a different number of outer shell electrons as P3 elements have access to vacant d and f orbitals
  • nitrogen cannot do this as it is P2 so does not have access to d and f orbitals
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13
Q

Reaction of sodium chloride with H2SO4

A

NaCl + H2SO4 —> NaHSO4 + HCl

  • HCl has low oxidising power
  • not redox
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14
Q

Reaction of sodium bromide with H2SO4

A

NaBr + H2SO4 —> HBr + NaHSO4

2HBr + H2SO4 —> Br2 + SO2 + 2H2O

  • HBr has strong oxidising power
  • redox reaction
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15
Q

Reaction of sodium iodide with H2SO4

A

NaI + H2SO4 —> HI + NaHSO4

2HI + H2SO4 —> I2 + SO2 + 2H2O

6HI + H2SO —> 3I2 + S + 4H2O

8HI + H2SO4 —> 4I2 + H2S + 4H2O

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16
Q

What happens to reducing power as you descend group 7?

A
  • reducing power increases
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17
Q

Products and observations of NaF with H2SO4

A

HF - misty fumes

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18
Q

Products and observations of NaCl with H2SO4

A

HCl - misty fumes

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19
Q

Products and observations of NaBr with H2SO4

A

HBr - misty fumes
Br2 - brown fumes
SO2 - colourless gas with choking odour

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20
Q

Products and observations of NaI with H2SO4

A

HI - misty fumes
I2 - purple fumes and black ppt
H2S - colourless gas with egg smell
SO2 - colourless gas with choking odour
S - yellow ppt

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21
Q

Define isoelectronic

A

Same number of outer electrons used in bonding

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22
Q

Uses of hexagonal boron nitride

A
  • chemically inert
  • used in reaction vessels and crucibles
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23
Q

Similarities of boron nitride and graphite

A
  • layered structure
  • high melting point and boiling point
  • very strong
24
Q

Differences of boron nitride and graphite

A
  • layers in boron nitride line up - they are not offset
  • h-boron nitride does not conduct electricity because no delocalised electrons due to different electronegativities
25
Explain the isoelectric relationship between boron nitride and carbon
- adopt the same hexagonal structure due to the number of bonding outer electrons being equal in them
26
Why can electrons in boron nitride not be delocalised?
- difference in electronegativities holding onto electrons
27
Describe and explain reaction of CCl4 in water
- immiscible in water and cannot be hydrolysed - no vacant d-orbitals for reaction
28
PbCl4 reaction
- yellow fuming liquid - explodes at 105° before boiling
29
Why is meant by amphoteric?
- able to react as both an acid and base
30
Al3+ ion
- small and highly charged so will be extensively hydrated [Al(H2O)6]3+
31
Pb2+ with OH-
[Pb]2+ + OH- —> Pb(OH)2 Pb(OH)2 + 2OH- —> [Pb(OH)4]2-
32
Define disproportionation
When the same atom is both oxidised and reduced in the same reaction, forming products containing the element in two different oxidation states
33
Reaction of chlorine with cold NaOH
Cl2 + NaOH —> NaCl + NaClO + H2O Cl2 + OH- —> Cl- + ClO- + H2O
34
Chlorine with hot NaOH
3Cl2 + 6NaOH —> 5NaCl + NaClO3 + 3H2O 3Cl2 + 6OH- —> 5Cl- + ClO3- + 3H2O
35
Describe the oxides of carbon
- CO2 is most stable - CO is only stable compound to contain carbon in the +2 oxidation state - CO is a reducing agent as it easily becomes oxidised from +2 to +4
36
Describe oxides of lead
- PbO is the most stable oxide of lead - PbO2 acts as oxidising agent as it is easily reduced from +4 to +2 - PbO is amphoteric
37
Describe CCl4 and SiCl4
- tetrachlorides - CCl4 does not react with water due to lack of available d orbitals meaning octet cannot be expanded - SiCl4 reacts very quickly with water in a hydrolysis reaction due to available 3d orbitals
38
Reaction of KI with Pb2+
- bright yellow ppt of lead iodide
39
Shape of BF3
Trigonal planar
40
Shape of NH3
Trigonal pyramid
41
Role of lead oxide in the reaction with hydrochloric acid
Oxidising agent
42
Use for cubic boron nitride
Cutting instruments
43
Phosphorus is able to form two different chlorides, PCl3 and PCl5. Nitrogen is only able to form one chloride, NCl3. Explain this difference.
Phosphorus has vacant d and f orbitals so can expand its octet whereas nitrogen doesn’t so it can’t expand
44
Explain why iron has more than one common oxidation state in its compounds.
Energy of 4s and 3d orbitals are all similar therefore ionisation energy to remove the electrons are too
45
Explain why aluminium forms compounds that are electron deficient
- aluminium has 3 outer shell electrons - forms 3 covalent bonds - giving 6 outer shell electrons —> draw Al2Cl6 dimer
46
Aluminium chloride forms Al2Cl6 dimer using coord bonding. Explain why coord bonds form
- Al is electron deficient - Cl donates a lone pair
47
Properties of PbO and PbO2
- lead forms positive ions and strong ionic bonds - amphoteric oxides - PbO2 contains lead in +4 but its most stable in +2 so is easily reduced / oxidising agent
48
Equation for lead as an oxidising agent
PbO2 + 4HCl —> PbCl2 + Cl2 + 2H2O
49
Equations to show amphoteric properties of PbO
PbO + 2NaOH —> Na2PbO2 + H2O PbO + 2HNO3 —> Pb(NO3)2 + H2O
50
Describe the properties of CO and CO2
- weak forces between molecules so gaseous - acidic oxide CO2 + 2NaOH —> Na2CO3 + H2O
51
Equation showing CO as a reducing agent
CO + CuO —> Cu + CO2
52
What happens to Pb2+ and Cr3+ when excess NaOH is added?
They dissolve as they are amphoteric
53
F
54
Why is the reaction between HCl and HBr with H2SO4 so different?
Bromide is more easily oxidised than chloride as it is a stronger reducing agent
55
What colour ppt is silver chloride?
White
56
What does it mean if something is soluble but does not effervesce?
It’s a hydroxide or oxide
57
What lead salt is soluble?
Lead nitrate

A2 CHEM UNIT3 (9 decks)

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