The Group 15 Elements

1
Chapter 15

• The Group 15 Elements

2
The Elements
Nonmetallic, unreactive
Nonmetallic, reactive
Semimetallic
Weak metallic
Weak metallic
3
Group Trends
Element Appearance at STP Electrical Resistivity (??cm) Acid-base Properties of Oxides
Nitrogen Colorless gas -- Acidic and neutral
Phosphorus White, waxy solid 1017 Acidic
Arsenic Brittle, metallic solid 33 Amphoteric
Antimony Brittle, metallic solid 42 Amphoteric
Bismuth Brittle, metallic solid 120 Basic
4
Group Trends
Element Melting Point (C) Boiling Point (C)
N2 -210 -196
P4 44 281
As Sublimes at 615 Sublimes at 615
Sb 631 1387
Bi 271 1564
5
Nitrogen Stability

• N?N
• 942 kJ/mol
• C?C
• 835 kJ/mol
• P?P
• 481 kJ/mol
• N-N
• 200 kJ/mol

6
Difference with Carbon

• N2H4(g) O2(g) ? N2(g) 2H2O(g)
• C2H4(g) 3O2(g) ? 2CO2(g) 2H2O(g)
• Hydrazine is much more reactive (explosive!)

7
Nitrogen Bonding

• Nitrogen normally only forms three bonds
• three ??
• two ?, one ?
• one ?, two ?

8
Phosphorus Bonding

• Phosphorus can form three or five bonds
• hypervalent compounds

9
NF3O vs. PF3O

• Difference is in the ability to ?-bond

10
Electronegativities

• Differing polarities between nitrogen and the
  others results in different reaction products
• Difference in hydride pH

Element Electronegativity
Nitrogen 3.0
Phosphorus 2.1
Arsenic 2.1
Antimony 1.9
Bismuth 1.8
NCl3(l) 3H2O(l) ? NH3(g) 3HClO(aq) PCl3(l)
3H2O(l) ? H3PO3(aq) 3HCl(g)
11
Nitrogen

• One allotrope
• colorless, odorless gas
• 78 atmospheric air
• inert diluent for reactive gases

12
Dinitrogen

• Not very soluble in water
• solubility increases with pressure

13
Dinitrogen Preparation

• Industrially
• distillation of air
• N2 b.p. -196C
• O2 b.p. -183C
• Laboratory
• warming ammonium nitrite
• NH4NO2(aq) ? N2(g) 2H2O(l)

14
Dinitrogen Uses

• 60 million tons annually
• inert atmosphere
• steel production
• oil refineries
• refrigerant
• reactant
• 6Li(s) N2(g) ? 2Li3N(s)
• O2(g) N2(g) ? 2NO2(g)
• 3H2(g) N2(g) ? 2NH3(g)

15
Overview of Nitrogen Chemistry

• Oxidation state is very pH dependant

1. N2 is very thermodynamically stable
2. High and to the left are strongly oxidizing
3. High and to the right are strongly reducing
4. Species on a convex curve tend to dispropotionate

16
Ammonia

• colorless, poisonous gas with a strong smell
• only common, basic gas
• very soluble in water
• ½ g NH3 per g H2O
• solutions are not really ammonium hydroxide
• NH3(aq) H2O(l) ? NH4(aq) OH-(aq)

17
Ammonia Reactions

• Laboratory preparation
• 2NH4Cl(s) Ca(OH)2(s) ? CaCl2(s) 2H2O(l)
  2NH3(g)
• Burns in air by two different pathways
• 4NH3(g) 3O2(g) ? 2N2(g) 6H2O(l)
• 4NH3(g) 5O2(g) Pt(cat.) ? 4NO(g) 6H2O(l)

18
Ammonia Reactions

• As a reducing agent
• with excess ammonia
• 2NH3(g) 3Cl2(g) ? N2(g) 6HCl(g)
• NH3(g) HCl(g) ? NH4Cl(s)
• with excess chlorine
• NH3(g) 3Cl2(g) ? NCl3(l) 3HCl(g)

19
Ammonia Reactions

• As a Brønsted base
• reacts with acids to produce ammonium salts
• 2NH3(aq) H2SO4(aq) ? (NH4)2SO4(aq)
• NH3(g) HCl(g) ? NH4Cl(g)
• As a Lewis base
• NH3(g) BF3(g) ? F3BNH3(s)
• 6NH3(aq) Ni(OH2)62(aq) ? Ni(NH3)62(aq)
  6H2O(l)

20
Ammonia as a Solvent

• Has a relatively high b.p. (-35C)
• due to hydrogen bonding
• Undergoes autoinonization
• 2NH3(l) ? NH4(NH3) NH2-(NH3)
• gives rise to a vast variety of acid-base
  chemistry

21
The Haber Process

• Fritz Haber and Walther Nernst
• N2(g) 3H2(g) ? 2NH3(g)
• both worked to find the best temperature and
  pressure combination to maximize yields

22
The Haber-Bosch Process

• Obtaining of pure gases
• purification of a hydrocarbon gas
• ZnO(s) H2S(g) ? ZnS(s) H2O(g)
• steam reforming process
• CH4(g) H2O(g) ? CO(g) 3H2(g)
• air is added to produce a mixture of nitrogen and
  hydrogen
• CH4(g) 1/2O2(g) 2N2(g) ? CO(g) 2H2(g)
  2N2(g)

23
The Haber-Bosch Process

• water gas shift process
• CO(g) H2O(g) ? CO2(g) H2(g)
• removal of carbon dioxide
• CO2(g) K2CO3(aq) ? 2KHCO3(aq)
• catalyzed Haber reaction
• N2(g) 3H2(g) ? 2NH3(g)

24
Ammonia Production and Use

• 1000 tons/day per plant
• 30-85 GJ/ton energy consumption
• Main use is in the fertilizer industry
• 2NH3(g) H2SO4(aq) ? (NH4)2SO4(aq)
• 3NH3(g) H3PO4(aq) ? (NH4)3PO4(aq)

25
The Ammonium Ion

• Most common nonmetallic cation used
• behaves like an alkali metal
• similar in size to potassium
• hydrolyzes
• NH4(aq) H2O(l) ? H3O(aq) NH3(aq)
• dissociates
• NH4Cl(s) ? HCl(g) NH3(aq)
• oxidizes
• NH4NO2(aq) ? N2(g) 2H2O(l)

26
Other Nitrogen Hydrides

• Hydrazine
• N2H4
• fuming, colorless liquid
• weak base
• N2H4(aq) H3O(aq) ? N2H5(aq) H2O(l)
• strong reducing agent
• N2H4(aq) 2I2(aq) ? 4HI(aq) N2(g)

27
Other Nitrogen Hydrides

• Hydrazine
• as rocket fuel
• dimethyl hydrazine
• (CH3)2NNH2
• reacts to identify carbonyl groups (CO)
• dinitrophenylhydrazine
• H2NNHC6H3(NO2)2

28
Other Nitrogen Hydrides

• Hydrogen azide
• HN3
• colorless, acidic liquid
• HN3(aq) H2O(l) ? H3O(aq) N3-(aq)
• poisonous and explosive
• 2HN3(l) ? H2(g) 3N2(g)

29
Azide Uses

• Air bags
• 2NaN3(s) ? 2Na(l) 3N2(g)
• 10Na(l) 2KNO3(s) ? 2K2O(s) 5Na2O(s) N2(g)
• 2K2O(s) SiO2(s) ? K4SiO4(s)
• 2Na2O(s) SiO2(s) ? Na4SiO4(s)

30
Azide Uses

• Lead(II) azide is a detonator in dynamite
• Pb(N3)2(s) ? Pb(s) 3N2(g)

31
Nitrogen Oxides

• Dinitrogen oxide, nitrous oxide
• N2O
• sweet, gaseous compound
• anesthetic, laughing gas
• used as a propellant in pressurized cans

32
Nitrogen Oxides

• Dinitrogen oxide
• only common gas besides oxygen to support
  combustion
• N2O(g) Mg(s) ? MgO(s) N2(g)
• prepared by heating ammonium nitrate
• NH4NO3(aq) ? N2O(g) 2H2O(l)

33
Nitrogen Oxides

• Nitrogen monoxide, nitric oxide
• NO
• colorless, neutral gas
• bond order of ½
• forms N2O2 when cooled
• readily loses an electron to form the nitrosyl
  ion, NO

34
Nitrogen Oxides

• Nitrogen monoxide
• prepared by nitrogen and oxygen
• N2 (g) O2(g) ? 2NO(g)
• prepared by reaction between copper and nitric
  acid
• 3Cu(s) 8HNO3(aq) ? 3Cu(NO3)2(aq) 4H2O(l)
  2NO(g)
• easily contaminated with nitrogen dioxide
• 2NO(g) O2(g) ? 2NO2(g)

35
Nitrogen Oxides

• Nitrogen monoxide
• helps dilate blood vessels
• memory
• synthesized in the body by enzymes

Viagra When NO means YES!
36
Nitrogen Oxides

• Dinitrogen trioxide
• N2O3
• dark, blue liquid

37
Nitrogen Oxides

• Dinitrogen trioxide
• acidic oxide gives nitrous acid

38
Nitrogen Oxides

• Nitrogen dioxide and dinitrogen tetraoxide
• NO2 (red-brown) and N2O4 (colorless)

39
Nitrogen Oxides

• Nitrogen dioxide and dinitrogen tetraoxide
• prepared by reaction of copper with nitric acid
• Cu(s) 4HNO3(l) ? Cu(NO3)2(aq) 2H2O(l)
  2NO2(g)
• prepared by heating metal nitrates
• Cu(NO3)2(s) ? CuO(s) 1/2O2(g) 2NO2(g)
• prepared from reaction of NO with O2
• 2NO(g) O2(g) ? 2NO2(g)

40
Nitrogen Oxides

• Nitrogen dioxide
• acidic oxide to form nitric and nitrous acids
• 2NO2(g) H2O(l) ? HNO3(aq) HNO2(aq)

41
Nitrogen Oxides

• Dinitrogen pentoxide
• N2O5
• colorless,deliquescent solid

42
Nitrate Radical

• Highly reactive free radical (0.1 to 1 ppb)
• formed from reaction of nitrogen dioxide with
  oxygen
• NO2(g) O2(g) ? NO3(g) O2(g)
• photolysed by sunlight
• NO3(g) h? ? NO(g) O2(g)
• NO3(g) h? ? NO2(g) O(g)

43
Nitrate Radical

• abstracts hydrogen atoms from alkanes to produce
  hydrocarbon radicals
• NO3(g) RH(g) ? R(g) HNO3(g)
• peroxyacetyl nitrate (PAN)
• CH3COO2NO3
• eye irritant in smog

44
Nitrogen Halides

• Nitrogen trichloride
• NCl3
• yellow, oily liquid
• explosive when pure
• sweat of the devil
• reacts with water
• NCl3(aq) 3H2O(l) ? NH3(g) 3HClO(aq)

45
Nitrogen Halides

• Nitrogen trifluoride
• NF3
• colorless, odorless gas
• low reactivity
• only reacts with oxygen
• 2NF3(g) O2(g) ? 2NF3O(g)

46
Nitrous Acid

• HNO2
• unstable, weak acid
• formed from mixing of a metal nitrite with an
  acid
• Ba(NO2)2(aq) H2SO4(aq) ? 2HNO2(aq) BaSO4(s)

47
Nitrous Acid

• disproportionates to nitric acid, nitrogen
  monoxide, and water
• 3HNO2(aq) ? HNO3(aq) 2NO(g) H2O(l)
• 2NO(g) O2(g) ? 2NO2(g)
• used to synthesize diazonium salts
• C6H5NH2(aq) HNO2(aq) HCl(aq) ? C6H5N2Cl-(s)
  2H2O(l)

48
Nitric Acid

• HNO3
• colorless, oily liquid
• strong oxidizing agent
• decomposes by light
• 4HNO3(aq) ? 4NO2(g) O2(g) 2H2O(l)
• 70 solution in water (16M)

49
Nitric Acid

• can be prepared from nitrogen, oxygen, and water
• 1/2N2(g) 5/4O2(g) 1/2H2O(g) ? HNO3(g)
• now produced by the Ostwald Process in three
  steps

50
Ostwald Process
51
Nitrites

• NO2-
• weak oxidizing agent

52
Nitrites

• Used as a meat preservative
• inhibits the growth of bacteria
• reacts with hemoglobin to make a bright red
  compound

53
Nitrates

• NO3-
• nitrates of every metal are known
• all are water soluble

54
Nitrates

• NH4NO3
• 1.5 x 107 tons produced annually
• NH3(g) HNO3(aq) ? NH4NO3(aq)
• used in cold packs
• NH4NO3(aq) ? NH4(aq) NO3-(aq) ?H 26
  kJ/mol

55
Nitrates

• NH4NO3
• decomposes at high temperatures
• 2NH4NO3(s) ? 2N2(g) O2(g) 4H2O(l)
• Other nitrates
• decomposition
• 2NaNO3(l) ? 2NaNO2(s) O2(g)
• 2Cu(NO3)2(s) ? 2CuO(s) 4NO2(g) O2(g)

56
Nitrates

• Testing for presence
• Devardas alloy
• alloy of aluminum, zinc and copper
• NO3-(aq) 6H2O(l) 8e- ? NH3(g) 9OH-(aq)
• brown ring test
• NO3-(aq) 4H(aq) 3e- ? NO(g) 2H2O(l)
• Fe(OH2)62(aq) NO(g) ? Fe(OH2)5NO2(aq)
  H2O(l)

57
Nitrogen Reactivity Flowchart
58
Phosphorus vs. Nitrogen
59
Phosphorus Allotropes

• White phosphorus
• P4
• poisonous, white, waxy substance

P4(s) 5O2(g) ? P4O10(s)
60
Phosphorus Allotropes

• Red phosphorus
• linear, polymeric form of P4
• stable in air to 400C

61
Phosphorus Allotropes

• Black phosphorus
• complex, polymeric form of P4
• most thermodynamically stable

62
Industrial Extraction of Phosphorus

• Ca3(PO4)2 rock
• central Florida
• Morocco-Sahara region
• Nauru Pacific island

63
Industrial Extraction of Phosphorus

• 2Ca3(PO4)2(s) 6SiO2(s) 10C(s) --gt 6CaSiO3(l)
  10 CO(g) P4(g)
• 10CO(g) 5O2(g) ? 10CO2(g)

Required Produced
10 tons phosphate rock 1 ton white phosphorus
3 tons sand 8 tons slag
1 ½ tons coke ¼ ton iron phosphides
14 MWh electricity 0.1 ton filter dust
2500 m3 flue gas
64
Matches

• 1012 matches consumed annually
• First match produced in 1833 with white
  phosphorus
• phossy jaw killed many workers

65
Matches

• In 1848, red phosphorus was found to be just as
  ignitable as white phosphorus
• half the reactants were on the tip, the other
  half on a strip on the box
• head contains KClO3 and the strip contains red
  phosphorus and Sb2S3

66
Phosphine

• PH3
• colorless, highly poisonous gas
• much less polar than ammonia
• does not hydrogen bond
• prepared from metal phosphides and water
• Ca3P2(s) 6H2O(l) ? 2PH3(g) 3Ca(OH)2(aq)

67
Phosphorus Oxides

• P4O6
• P4(s) 3O2(g) ? P4O6(s)
• P4O10
• P4(s) 5O2(g) ? P4O10(s)
• P4O10(s) 6H2O(l) ? 4H3PO4(l)

68
Phosphorus Chlorides

• PCl3
• P4(s) 6Cl2(g) ? 4PCl3(l)
• PCl5
• P4(s) 10Cl2(g) ? 4PCl5(l)

69
Phosphorus Chlorides

• PCl3 vs. NCl3 reactions in water
• PCl3(l) 3H2O(l) ? H3PO3(l) 3HCl(g)
• NCl3(l) 3H2O(l) ? NH3(g) 3HClO(aq)
• Converts alcohols to chloro compounds
• PCl3(l) 3C3H7OH(l) ? 3C3H7Cl (g) H3PO3(l)
• PCl5 reaction in water
• PCl5(l) H2O(l) ? POCl3(l) 2HCl(g)
• POCl3(l) 3H2O(l) ? H3PO4(l) 3HCl(g)

70
Phosphorus Oxychloride

• POCl3
• 2PCl3(l) O2(g) ? 2POCl3(l)
• used to make phosphates
• fire retardants
• solvents for separating uranium from plutonium

TBP
71
Phosphorus Oxyacids

• Three common oxyacids

Phosphonic acid phosphorous acid diprotic
Phosphoric acid triprotic
Phosphinic acid hydrophosphorous acid monoprotic
72
Phosphorus Oxyacids

• Phosphoric acid
• 14.7 M concentrated solution, syrupy due to
  hydrogen bonding
• triprotic
• H3PO4(aq) H2O(l) ? H3O(aq) H2PO4-(aq)
• H2PO4-(aq) H2O(l) ? H3O(aq) HPO42-(aq)
• HPO42-(aq) H2O(l) ? H3O(aq) PO43-(aq)

73
Phosphorus Oxyacids

• Phosphoric acid
• thermal preparation process
• P4(s) 5O2(g) ? P4O10(s)
• P4O10(s) 6H2O(l) ? 4H3PO4(l)
• wet preparation process
• Ca3(PO4)2(s) 3H2SO4(aq) ? 2H3PO4(aq) 3CaSO4(s)

74
Phosphorus Oxyacids

• Phosphoric acid
• can undergo polymerization upon heating

75
Phosphorus Oxyacids

• Phosphoric acid
• Uses
• fertilizers
• soft drink additive
• metal poisoning
• rust removers

76
Phosphates

• Most are insoluble
• except alkali metal and ammonium phosphates
• Phosphate ion undergoes hydrolysis
• PO43-(aq) H2O(l) ? HPO42-(aq) OH-(aq)
• Uses
• household cleaners
• detergents
• Pasteurization of cheese
• fire retardants

77
Phosphates

• Baking soda
• Ca(H2PO4)2(aq) NaHCO3(aq) ? CaHPO4(aq)
  NaH2PO4(aq) CO2(g) H2O(g)
• Fertilizers
• Ca3(PO4)2(s) 2H2SO4(aq) ? Ca(H2PO4)2(s)
  2CaSO4(s)

78
Biological Aspects

• Nitrogen
• nitrogen cycle 108 tons of nitrogen cycled a
  year

79
Biological Aspects

• Phosphorus
• phosphorus cycle

80
Biological Aspects

• Arsenic
• minute amount is essential to life
• any more is quite toxic
• found naturally in many water deposits
• Bangladesh
• an arsenic compound was the original chemical
  that started chemotherapy

81
Biological Aspects

• Bismuth
• The Medicinal Element
• treatment of syphilis and tumors
• Pepto-Bismol and De-Nol
• bismuth subsalicylate and bismuth subcitrate
• bactericides