16th Group Flashcards

1
Q

Common electronic configuration

A

ns2 np4

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2
Q

Valences

A

2 & 4 (but O differs)

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3
Q

What are the metallic characters of 16th group elements

A

O and S are non-metals

Se, Te, Po show both metal and non-metal characters

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4
Q

What is the only element in 16th group which exists in gaseous state?

A

O

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5
Q

Oxidation states

A

Except O, other elements in the group can form even numbered oxidation states from -2 upto +6

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6
Q

What are the 16th group hydrides?

A

H2O
H2S
H2Se
H2Te

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7
Q

2 allotropic forms of oxygen

A

O2 and O3

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8
Q

Describe O3

A

Ozone is a light blue colored (colorless) gas with a pungent odor

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9
Q

What special properties does O3 have due to its ability to produce atomic oxygen?

A
  1. Oxidizing agent
  2. Reducing agent
  3. Disinfecting agent
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10
Q

Describe O2

A

O2 is colorless, and odorless

Slightly water soluble

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11
Q

How is O2 prepared in the laboratory?

A

Catalytic decomposition of KClO3

KClO3 ———-> KCl + O2

(heating with MnO2 or Pt)

Catalytic decomposition of H2O2

H2O2 ——-> H2O + O2

(heating with MnO2)

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12
Q

How is O2 produced industrially?

A

By fractional distillation of liquid air

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13
Q

What is the most widely used solvent?

A

water

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14
Q

Show the ionization of H2O

A

2H2O —> OH- + H30+

revers.

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15
Q

Show water’s reactions with acids and bases

A

NH3 + H2O —> NH4+ + OH-

HCl + H20 —–> Cl- + H3O+

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16
Q

water’s reaction w bases

A

NH3 + H2O —> NH4+ + OH-

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17
Q

water’s reaction w acids

A

HCl + H20 —–> Cl- + H3O+

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18
Q

Why is water considered amphiprotic?

A

It can either donate or accept a proton

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19
Q

Decomposition of H2O2 in sunlight

A

H2O2 —>H2O + O2

So, H2O2 is usually stored in brown or black colored bottles

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20
Q

Describe H2O2

A
  • viscous, colorless liquid
  • compared to water, MP, BP and density higher. This is due to presence of OH groups
  • Due to excess mass, comparatively stronger London forces are also possible.
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21
Q

How does H2O2 release atomic oxygen

A

H2O2 —-> H2O + O

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22
Q

uses of H2O2

A

Oxidizing agent
Disinfecting agent
Bleaching agent
Reducing agent
Used as a rocket fuel

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23
Q

Properties of H2O2

A
  1. Oxidizing agent
  2. Reducing agent
  3. Antiseptic agent
  4. Bleaching agent
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24
Q

How does H2O2 react as an oxidizing agent?

A
  1. with acidified iodide ions

H2O2 —> H2O
I- —> I2

  1. Reaction with Fe2+ ions

H2O2 —> H2O
Fe2+ —> Fe3+

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25
Q

How does H2O2 react with acidified iodide
ions

A
  1. with acidified potassium ions

H2O2 —> H2O
I- —> I2

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26
Q

How does H2O2 react with Fe2+ ions

A
  1. Reaction with Fe2+ ions

H2O2 —> H2O
Fe2+ —> Fe3+

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27
Q

How does H2O2 act as a reducing agent?

A
  1. Reaction w/ acidified KMnO4

MnO4- —–> Mn2+
violet colorless
H2O2 —> O2

  1. Reaction w/ acidified K2Cr2O7

Cr2O72- —-> Cr3+
orange green
H2O2 —–> O2

  1. Reaction w/ MnO2

MnO2 –> Mn2+
brown colorless
H2O2 —> O2

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28
Q

Reaction of H2O2 w/ MnO2

A

MnO2 –> Mn2+
brown colorless
H2O2 —> O2

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29
Q

Reaction of H2O2 w/ acidified K2Cr2O7

A

Cr2O72- —-> Cr3+
orange green
H2O2 —–> O2

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30
Q

Reaction of H2O2 w/ acidified KMno4

A

MnO4- —–> Mn2+
violet colorless
H2O2 —> O2

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31
Q

Describe Sulphur

A
  • has a high ability to produce chain structures/cyclic structures by joining sulphur atoms together by single bonds
  • so, it can form a higher no. of allotropic forms
  • they can be classified into 2 main types: crystalline sulphur and non-crystalline sulphur
  • crystalline sulphur: rhombic s. (alpha s.) and monoclinic s. (beta s.)
  • amorphous sulphur: plastic s. and colloidal s
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32
Q

2 types of S

A

crystalline sulphur
non-crystalline sulphur

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33
Q

2 types of crystalline sulphur

A

rhombic s. (alpha s.) and monoclinic s. (beta s.)

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34
Q

2 types of non-crystalline sulphur

A

plastic s. and colloidal s

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35
Q

How are crystalline sulphur formed?

A

s8 rings

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36
Q

What’s the most stable form of crystalline sulphur?

A

Rhombic sulphur (stable below 95C)

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37
Q

When is monoclinic sulphur stable?

A

Above 95C

38
Q

How can monoclinic s. be prepared?

A

by cooling molten sulphur slowly

39
Q

another name for colloidal sulphur

A

milk of sulphur

40
Q

Oxidation no.s of sulphur

A

-2 to +6

41
Q

show reducing reactions of s

A

S + O2 —> SO2

S + hot conc. H2SO4 —-> SO2 + H2O

S+ hot conc. HNO3 —–? H2SO4 + NO2 + H2O

42
Q

disproportioning of S

A

S + NaOH ——> Na2S + Na2S2O3 + H2O

43
Q

uses of sulphur

A
  • good fungicide
  • manufacturing medicinal drugs for skin diseases
  • used in sulphuric manufacturing process
  • used in rubber vulcanization
44
Q

Oxoacids of S

A

H2SO4

H2S

H2S2O3

45
Q

Describe H2SO4

A

Strong, diprotic acid

46
Q

How is H2SO4 produced?

A

SO3 + H20 ——> H2SO4

47
Q

ionization of H2SO4

A

H2SO4 + H2O ——> HSO4- + H3O+

HSO4- + H20 ——-> SO42- + H3O+

48
Q

Properties of H2SO4

A

Dil. H2SO4 —-> STRONG ACID

CONC. H2SO4 ——> STRONG OXIDIZING AGENT
STRONG DEHYDRATING AGENT

49
Q

Show H2SO4 reactions as a strong acid

A

H2SO4 + 2H2O —-> SO42- + H3O+

dil. H2SO4 acts as a strong acid and gives 2 protons as above

50
Q

H2SO4 reactions as a strong oxidizing agent

A
  1. reactions w/ metals

Mg + conc. H2SO4 ———> MgSO4 + SO2 + H2O

Cu + conc. H2SO4 ——–> CuSO4 + SO2+ H2O

  1. reactions w/ non-metals

S + Conc. H2SO4 ——–> SO2 + H2O

C + conc. H2SO4 ———> CO2 + SO2 + H2O

51
Q

Reactions of H2SO4 with metals

A

Mg + conc. H2SO4 ———> MgSO4 + SO2 + H2O

Cu + conc. H2SO4 ——–> CuSO4 + SO2+ H2O

52
Q

Reactions of H2SO4 with non-metals

A

S + Conc. H2SO4 ——–> SO2 + H2O

C + conc. H2SO4 ———> CO2 + SO2 + H2O

53
Q

Why does H2SO4 have a dehydrating property?

A

It has the ability to remove H and O in a 2:1 ration from a compound

54
Q

reactions of H2SO4 as a dehydrating agent

A

C6H12O6 ———-> 6C + 6H2O

C2H5OH ——-> C2H4 + H2O

in presence of conc. H2SO4

55
Q

Describe H2SO3

A
  • weak, diprotic acid
  • Reactions of SO2 w/ water makes H2SO3
  • unstable
  • can dissociate into SO2 + H2O
56
Q

Describe H2S2O3

A
  • acid unstable, but salts of H2S2O3 are stable
  • It can decompose as below

H2S2O3 + H2O —-> S + SO2 + H2O

Na2S2O3 + HCl ——–> NaCl + S + SO2 + H2O

57
Q

How does H2S2O3 help iodometric titrations

A

S2O32- ion can act as a reducing agent.

I2 + S2O32- ——-> I- + S4O62-

58
Q

Describe H2S

A
  • Colorless, toxic gas with odor of rotten eggs
  • Weakly acidic
  • H2S burns in air with a blue flame to give H2O and SO2
59
Q

Preparation of H2S

A

Reaction of a metal sulphide with a strong acid

FeS + HCl ——> H2S + FeCl2

60
Q

Identification of H2S

A

When H2S is allowed to pass through a filter paper moistened with Pb(CH3COOH) it turns black due to formation of PbS

Pb(CH3COOH) + H2S —> PbS + CH3COOH

We can also use Pb(NO3)2, AgNO3 and CuSO4 for this

Pb(NO3)2 + H2S ——> PbS + HNO3

AgNO3 + H2S ——-> Ag2S + HNO3

CuSO4 + H2S ——> CuS + H2SO4

61
Q

Reactions of H2S identification

A

Pb(CH3COOH) + H2S —> PbS + CH3COOH

Pb(NO3)2 + H2S ——> PbS + HNO3

AgNO3 + H2S ——-> Ag2S + HNO3

CuSO4 + H2S ——> CuS + H2SO4

62
Q

Properties of H2S

A
  1. Boiling point of H2S is less than H2O
  2. H2S EXISTS AS A GAS while water exists as a liquid at room temperature
  3. Acidic character
  4. Oxidizing character
  5. Reducing character
  6. Forms salts with bases
63
Q

Why is boiling point of H2S < H2O

A

H2O has O-H bonds while H2S has S-H bonds. So, H bonds are possible between H2O molecules and dipole-dipole interactions are possible in-between H2S molecules.

64
Q

Describe H2S acidic character

A

H2S is a weak, diprotic acid

Partially dissociates as follows

H2S + H2O ———> HS- + H3O+

HS- + H2O ———–> S2- + H3O+

revers.

Following evidences can be given for the acidic nature of H2S

Na + H2S (EXCESS) ———> NaHS + H2

Na (EXCESS) + H2S ———-> Na2S + H2

65
Q

Evidences for acidic nature of H2S

A

Na + H2S (EXCESS) ———> NaHS + H2

Na (EXCESS) + H2S ———-> Na2S + H2

66
Q

How does H2S form salts with bases

A

NaOH + H2S (EXCESS) ———> NaHS + H2O

NaOH (EXCESS) + H2S ———-> Na2S + H2O

67
Q

Examples for reducing property of H2S

A

H2S ——> S

  1. Reaction w/ KMnO4

MnO4- ——-> Mn2+
violet colorless
S2- ——–> S

  1. Reaction w/ K2Cr2O7

Cr2O72- ——-> Cr3+
orange green

S2- ———-> S

forms a turbid green solution

  1. Reaction w/ Na3AsO4

AsO43- ——> As3+

S2- ——–> S

  1. Reaction w/ Cl solution

Cl2 ——-> Cl-

S2- ——–> S

  1. Reaction w Br

Br2 ——> Br-
(brown) (colorless)
S2- ——> S

  1. Reaction w/ SO2

S2- ——–>S

SO2 ——-> S

68
Q

Reaction of H2S with KmnO4

A

MnO4- ——-> Mn2+
violet colorless
S2- ——–> S

69
Q

Reaction of H2S with K2Cr2O7

A

Cr2O72- ——-> Cr3+
orange green

S2- ———-> S

forms a turbid green solution

70
Q

Reaction of H2S with Na3AsO4

A

AsO43- ——> As3+

S2- ——–> S

71
Q

Reaction of H2S with Cl solution

A

Cl2 ——-> Cl-

S2- ——–> S

72
Q

Reaction of H2S with Br solution

A

Br2 ——> Br-
(brown) (colorless)
S2- ——> S

73
Q

Reaction of H2S with SO2 solution

A

S2- ——–>S

SO2 ——-> S

74
Q

Show oxidizing property of H2S

A

H2S —–> H2

  1. Reaction w/ Na

H2S —-> H2
Na —-> Na2S

  1. Reaction with Mg

H2S —–> H2
Mg ——> MgS

75
Q

Reaction of H2S with Na

A

H2S —-> H2
Na —-> Na2S

76
Q

Reaction of H2S with Mg

A

H2S —–> H2
Mg ——> MgS

77
Q

Describe SO2

A
  • a colorless gas with a pungent or choking smell
  • poisonous
78
Q

preparation of SO2

A
  1. Reaction of solid sulphide with a dilute acid

SO32- + H+ ———> SO2 + H2O

  1. Reaction of S with conc. H2SO4

S + H2SO4 ——-> SO2 + H2O

  1. Reaction of Cu with conc. H2SO4

Cu + H2SO4 ———> CuSO4 + SO2 + H2O

  1. Adding a dilute acid to a thiosulfate

Na2S2O3 + HCl ——> NaCl + SO2 + S + H2O

79
Q

Adding a dilute acid to a thiosulfate

A

Na2S2O3 + HCl ——> NaCl + SO2 + S + H2O

80
Q

Reaction of Cu with conc. H2SO4

A

Cu + H2SO4 ———> CuSO4 + SO2 + H2O

81
Q

Reaction of S with conc. H2SO4

A

S + H2SO4 ——-> SO2 + H2O

82
Q

Reaction of solid sulphide with a dilute acid

A

SO32- + H+ ———> SO2 + H2O

83
Q

Identification of SO2

A

SO2 is allowed to pass through a filter paper moistened with K2Cr2O7.

Then formation of green coloured dots can be seen.

Or, SO2 gas can be passed through acidic K2Cr2O7 and the solution will turn green color

84
Q

Properties of SO2

A
  1. Acidity
  2. Bleaching property
  3. Oxidizing property
  4. Reducing property
85
Q

Show Acidity of SO2

A

SO2 produces sulfurous acid as below

SO2 (S) ———-> SO2 (aq.)

SO2 + H2O ———-> H2SO3 (reversible)

The acidic property of SO2 is evident by following reaction

SO2 + NaOH ——> Na2SO3 + H2O

EXCESS SO2 + NaOH ——> NaHSO3

86
Q

Show the acidic property of SO2

A

SO2 + NaOH ——> Na2SO3 + H2O

EXCESS SO2 + NaOH ——> NaHSO3

87
Q

Show reducing property of SO2

A

SO2 ——> SO42-

  1. Reaction of acidified KMnO4

SO2 ——> SO42-

MnO4- ——> Mn2+

  1. Reaction of acidified K2Cr2O7

SO2 ——-> SO42-

Cr2O72- ———> Cr3+

  1. Reaction of FeCl3

Fe3+ ——–> Fe2+

SO2 ———-> SO42-

88
Q

Reaction of SO2 with KMnO4

A

SO2 ——> SO42-

MnO4- ——> Mn2+

89
Q

Reaction of SO2 with FeCl3

A

Fe3+ ——–> Fe2+

SO2 ———-> SO42-

90
Q

Reaction of SO2 with K2Cr2O7

A

SO2 ——-> SO42-

Cr2O72- ———> Cr3+

91
Q

Show oxidizing property of SO2

A

SO2 ——–> S

  1. Reaction w H2S

SO2 —> S
H2S —> S

  1. Reaction w heated metals

Mg + SO2 —–> Mgo + MgS
Fe + SO2 ——-> FeO + FeS

92
Q

Reaction of SO2 with heated metals

A

Mg + SO2 —–> Mgo + MgS
Fe + SO2 ——-> FeO + FeS