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P Block 12th > Oxygen Group > Flashcards

Oxygen Group Flashcards

1
Q

Describe elements of the Oxygen group.

A

O - Most abundant element in Earth’s crust.
S - exists in the form of sulphate
Gypsum - CaSO4.2H2O
Epsom salt - MgSO4.7H2O
Baryte - BaSO4
Galena - PbS, Zinc blende - ZnS and copper pyrite - CuFeS2
Se and Te - Metal sellerides and tellurides
Po - decay product of uranium and thorium

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2
Q

Atomic size

A

O<S<Se<Te<Po

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3
Q

Ionisation energy

A

O>S>Se>Te>Po

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4
Q

Electron gain enthalpy

A

S>Se>Te>O

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5
Q

Electronegativity

A

O>S>Se>Te>Po

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6
Q

Metallic Character

A

O<S<Se<Te<Po

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7
Q

M.P. and B.P. order

A

O<S<Se<Te
Large difference between M.P. and B.P. O and S

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8
Q

Physical properties of the oxygen group.

A

O and S - Non metal
Se and Te - Metalloid
Po - Metal (radioactive)
O,S,Se and Te show allotropy

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9
Q

Show oxidation states of the oxygen group.

A

O - -2,+2
S - -2,+2,+4,+6
Se - -2,+2,+4,+6
Te - -2,+2,+4,+6
Po - +2,+4

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10
Q

Anomalous behaviour of Oxygen

A

Small size and high IE and high EN
H2O - Hbond
H2S,H2Se and H2Te - Don’t show H bond
Max. Covalency is 4 (absence of d orbitals)
D orbital is present in all other elements

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11
Q

Reactivity of H

A

Acidic character - H2O<H2S<H2Se<H2Te
Reducing nature - H2O<H2S<H2Se<H2Te
Thermal stability - H2O>H2S>H2Se>H2Te
M.P. and B.P. - H2O>H2S>H2Se>H2Te

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12
Q

In which elements mono halide exists as dimer and how these dimers disproportionate.

A

S2F2,S2Cl2,S2Br2,Se2Cl2,Se2Br2
Disproportionation reaction
Se2Cl2 ➡️ Se + SeCl4

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13
Q

Show preparation of Dioxygen.

A

Heating oxygen containing salt (chlorate, nitrate and permangnate)
Heat
2KClO3 ➡️ 2KCl + 3O2
MnO2
Thermal decomposition of less reactive metal oxide
Ag2O ➡️ Ag + O2
HgO ➡️ Hg + O2
Pb3O4 ➡️ PbO + O2
PbO2 ➡️ PbO + O2
Decomposition of H2O2 by catalyst
2H2O2 ➡️ 2H2O + O2

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14
Q

Large scale preparation of Dioxygen.

A

Electrolysis of H2O (H2 gas - cathode)
(O2 gas - Anode)

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15
Q

Industrial preparation of Dioxygen.

A

Air ➡️ Remove CO2 and Water vapour ➡️ Remaining gas are liquified and upon fractional distillation gives N2 and O2

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16
Q

Show properties of O2.

A

Colourless, odourless
Liquifying temp. - 90K
Melting/Freezing temp - 55K
3 stable isotopes - O16, O17,O18
O2 - Paramagnetic

17
Q

Show some metal oxides with a high oxidation number being acidic.

A

Mn2O7
CrO3
V2O5

18
Q

Show preparation of ozone.

A

Steam of oxygen is passed through silent electric discharge
Conversion of O2 to O3 - is only 10%
O2 ➡️ O3 (ozonised oxygen) ∆H = +ve
If more than 10% ozone is required, a battery of ozoniser is used. Pure ozone is condensed in a vessel surrounded by liq.O2.

19
Q

Mention Properties of ozone.

A

Pure O3, pale blue gas, dark blue liq., violet black solid
O3 - thermodynamically unstable
O3 ➡️ O2
∆H = -ve
∆S = +ve
∆G = -ve (spontaneous reaction)

20
Q

Show depletion of ozone layer.

A

NO is emitted from supersonic jet aeroplane deplete ozone layer
NO + O3 ➡️ NO2 + O2
Use of freons deplete ozone layer

21
Q

Describe allotropes of sulphur.

A

Rhombic Sulphur (yellow)
Alpha sulphur (below 369)
Stable at room temp.
Alpha sulphur stable below 369K
Monoclinic sulphur (colourless)
Beta sulphur stable above 369K
At 369K both Alpha and beta sulphur stable.

22
Q

What is Alpha sulphur.

A

Roll sulphur + CS2 ➡️ Alpha sulphur
Insoluble in water
Partly dissolve in benzene, alcohol and ether
Soluble in CS2

23
Q

What is beta sulphur.

A

Soluble in CS2
Melting Alpha sulphur in a dish and cooling till crust is formed.
Two holes are made in the crust and the remaining liquid is poured out.
On removing crust needle shape beta sulphur is formed.

24
Q

Describe structure of Alpha and beta sulphur.

A

Both Alpha and beta sulphur are S8 molecules - Crown shape
S6 molecule - chair form
S2 - like O2

25
Q

Show preparation of SO2.

A

S + O2 ➡️ SO2 (6-8% SO3 is also formed)
Lab preparation
SO3 + H+ ➡️ H2O + SO2
Industrial preparation
Byproduct of roasting of sulphide ore
FeS2 + O2 ➡️ Fe2O3 + SO2

26
Q

Show certain reactions of SO2.

A

SO2 + H2O ➡️ H2SO3
SO2 + NaOH ➡️ Na2SO3 + H2O
Na2SO3 + SO2 ➡️ NaHSO3
Charcoal
SO2 + Cl2 ➡️ SO2Cl2
V2O5
SO2 + O2 ➡️ SO3
Moist SO2 acts as a reducing agent.

27
Q

Mention oxyacids of sulphur.

A

H2SO3 - Sulphurous acid
H2SO4 - Sulphuric acid
H2S2O8 - Peroxodisulphuric acid
H2S2O7 - Pyrosulphuric acid or Oleum

28
Q

Preparation of H2SO4.

A

Contact process - 3 step process
Burning of sulphur or sulphide ore
V2O5
SO2 + O2 ➡️ SO3
SO3 + H2O ➡️ H2SO4 - Not enough yield
SO3 + H2SO4 ➡️ H2S2O7 - Oleum
Dilution of Oleum with water yields H2SO4 of desired concentration
H2SO4 obtained by contact process - 96 to 98% pure

29
Q

State properties of H2SO4.

A

Conc.H2SO4 - Strong Dehydrating Agent
Conc.H2SO4
C12H22O11 ➡️ 12C + 11H2O
Hot Conc. H2SO4 - Moderate oxidising agent
Reduce SO2
Cu + Conc.H2SO4 ➡️ CuSO4 + SO2 + H2O
S + Conc.H2SO4 ➡️ SO2 + H2O
C + Conc.H2SO4 ➡️ CO2 + SO2 + H2O

P Block 12th (3 decks)

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