©B.S.S.PRASAD

EAMCET CHEMISTRY

93

NOBLE GASES •

The elements of zero group are called noble gases.

•

The noble gases are also called inert gases due to

formed is CuO and when passes over heated

their least reactivity.

Magnesium the compound formed is Mg3N2

•

•

Noble gases are also called rare gases due to their

In Ramsay and Rayleigh’s second method Oxygen and Nitrogen are removed from air as NO2 with the

The elements of Noble gases are Helium, Neon,

help of an electric arc. •

When an electric arc is struck in a large bulb

All the noble gases have an octet or ns2 np6

containing air, the compound that forms is Nitric

electronic configuration in their outer most shell

oxide. •

except Helium. 2

•

Helium has a dupet or ns electronic configuration.

•

The noble gas that is wrongly placed in p-block is

•

•

When air passes over heated copper, the compound

less abundance.

Argon, Krypton , Xenon. And Radon •

•

Nitric oxide on further oxidation gives Nitrogen dioxide.

•

In Ramsay and Rayleigh’s second method the

He

reagent used to remove NO2 is NaOH and to

All the noble gases except Helium have their

remove excess oxygen is alkaline solution of

differentiating electron entering in p-orbital.

pyrogallol. •

In Fischer and Ringe’s method the substance used

•

The radioactive noble gas is Radon

•

The noble gases are discovered by Ramsay and

to isolate noble gases from air is a mixture of

Rayleigh

Calcium carbide. and Calcium chloride

•

•

The Noble gas that was observed by Janssen and

•

Lockyer in a total solar eclipse was Helium.

heated Calcium carbide is Calcium cyanamide and

The name Helium is derived from “Helos” meaning

carbon.

Sun, Neon means New, Krypton means “Hidden”

•

•

•

The density of nitrogen isolated from air is higher

•

take place are:

the presence Argon in the atmosphere.

1) CaC2 + N2 → CaCN2 + C 2)C + O2 → CO2

The most abundant Noble gas in the air is Argon

3) 2C + O2 → 2CO

and the least abundant is Helium.

5) CO2 + 2KOH → K2CO3 + H2O

All the noble gases occur freely in their native form

•

Al the noble gases are colour less odour less gases

•

Isolation Of noble gases

•

The noble gases were, first separated from air by

4) CuO + CO → CO2 + Cu

The drying agents to remove moisture is conc H2SO4

•

In Dewar’s method, the technique used to isolate noble gases is “adsorption”

at room temperature

•

In Fischer and Ringe’s method the reactions that

than that obtained from chemical reaction is due to

as mono-atomic particles. •

. In Fischer and Ringe’s method O2 is removed as CO2.

and Xenon means “Stranger”. •

The compound that forms, when air is passed over

•

The apparatus used to isolate noble gases from air by Dewar’s method is called Dewar’s flask.

Ramsay and Rayleigh.

•

The Dewar’s flask is made up of coconut charcoal.

In the Ramsay and Rayleigh’s first method oxygen

•

The adsorption of a gas over activated charcoal increases as the molecular weight increases.

in the air is removed by passing over heated copper and Nitrogen is removed by passing over heated Magnesium. NOBLE GASES

•

At 173K, all the gases except He and Ne in the air are adsorbed over coconut charcoal.

©B.S.S.PRASAD

•

•

EAMCET CHEMISTRY

94

The temperature needed to adsorb Neon on

•

XeF4 is prepared by heating Xe with F2 in 1:5 ratio

Coconut charcoal is 93K.

•

XeF6 is prepared by heating Xe with F2 in 1:20

The apparatus used to separate noble gases from air

ratio

by fractional distillation is called “Claude’s

•

The products of hydrolysis of xenon fluorides are:

apparatus”

•

2XeF2 + 2H2O → 2Xe + 4Hf +O2

Separation of noble gases by fractional distillation

•

3XeF4 + 6H2O → 2Xe + XeO3 + 12 HF + 3/2 O2

depends on the difference in boiling points.

•

XeF6 + 6H2O → XeO3 +6Hf

•

The order of boiling points is:

•

When water is less: XeF6 +H2O → XeOF4 +2HF

•

He < Ne
•

XeF2 is an oxidizing agent. It oxidizes HCl to Cl2

•

All the noble gases are colourless odourless

•

and HI to I2

tasteless gases at room temperature. •

•

•

The Noble gases are least reactive due to their high

benzene to fluorobenzene.

Ionisation energy and almost negligible electron

•

H2 and Hg reduce XeF2 , XeF4 and XeF6 to Xenon.

affinity.

•

XeF6 when reacts with SiO2 give SiF4

In case Noble gases, the Atomic size, density,

Compound

solubility in water increase with increase of atomic weight. •

•

state XeF2

Linear

2

Square planar

atomic size.

Sp3d3

1

Distorted

XeO3

+6

Sp3

1

Pyramidal

XeO4

+8

Sp3

0

Tetrahedral

octahedral

The noble gases can form chemical compounds

Helium , due to lack of d-orbitals cannot form any

Among all the Noble gases, Xenon forms

The type of compound formed by trapping the

•

In XeF2, XeF4 and XeF6 the bonds are sigma bonds

•

In XeO3 the no. of σ bonds are 3 and no. of π bonds are3

•

•

Uses of Noble gases

•

He is used in gas thermometers, electrical transformers, Oxygen cylinders used by Scuba divers

Helium and Neon do not form any Clatharate compound due to small size.

•

Hospitals,

nuclear

reactors

and

Neon is used in Glow lamps and electrical relays and rectifiers

•

Compounds of Xenon Fluorides of Xenon are prepared by heating Xe

and

metallurgy

Compounds of noble gases can be formed by dipole-dipole interactions also.

In XeO4 the no. of σ bonds are 4 and no. of π bonds are4.

compounds”.

•

3

3 2

Sp d

molecules such as β- quinol are called “Clatharate

•

pairs Sp3d

+2

+6

noble gases in the crystal lattice of big organic

•

Shape

+4

low ionisation energy compared to others.

•

Lone

XeF4

compounds more easily due to its biggest size and

•

Hybrid.

XeF6

compound by excitation method. •

Oxidation

The Ionisation energy decreases with increase of

under excited state. •

XeF2 can be used as fluorinating agent. It converts

Krypton is used in Miner’s cap lamps, Devices used to measure thickness of metal sheets

•

Xenon is used in Photographic flash bulbs and in

with fluorine to about 400°C in a sealed Nickel

the detection of neutral mesons and γ-photons in

vessel .

bubble chambers.

XeF2 is prepared by heating Xenon with fluorine in 2:1 ratio

NOBLE GASES

•

Radon is used in treatment of cancer and to detect defects in metal castings.

©B.S.S.PRASAD

EAMCET CHEMISTRY

95 3. Vander Walls

Exercise

4. All

12. XeF2 is iso- structural with 1. Which of the following cannot form a clatharate? 1. Xenon

2. Helium

3. Argon

4. All

2. The correct order of atomic radius is 1. O>F>Ne

2. O
3. O>F
4. ONe

3. Which can be easily liquefied among the following? 1. Xe

2. N2

3. O2

4. He

4. The weather balloons used by meteorologists use 1. He

2. H2

3. N2

4. O2

5. When air is passed over heated Calcium carbide, the products could be 2. Ca(CN)2 and CO2

3. NO2 and CO2

4. NO and CO

6. Which can be used to absorb un reacted oxygen in the separation on noble gases from air? 1. CuO

2. Pyrogallol

3. Mg

4. Cu

7. The compound formed, when N2 is passed over heated magnesium is

3. SCl2

4. CH2Cl2

13. The pair of compounds having same hybridisation on central atoms is 1. XeO3 and BF3

2. XeO4 and XeF4

3. XeF6 and SF6

4. XeO3 and CCl4

14. The compound with highest bond angle is 1. XeF2

2. XeF4

3. XeF6

4. XeO4

15. The ratio of Xe and F2 that give XeF2, when a mixture of Xe and F2 are heated together is 1. 1:2

2. 2:1

3. 1:20

4. 20:1

1. Dewar

2. Ramsay and Rayleigh

3. Cavendish

4. Fischer

17. A person suffering from Asthma should get breathing gas from 1. 100% O2

2. 100% He

3. 80% O2 and 20 %He

4. 80% He and 20% O2

18. When neon is used in a colourless tube of glow lamp the visible colour is

1. Magnesium nitrate

2. Magnesium nitrite

3. Magnesium nitride

3. All

8. Which of the following does not use any chemical methods in the separation of Noble gases from air? 1.

Ramsay and Rayleigh’s method

2.

Fischer and Ringe’s method

3.

Dewar’s method

4.

All the above

1. Golden yellow

2. Blue

3. Colourless

4. Orange red

19. The gas that flows up when cooled to very low temperature at normal pressure is called 1. Ne-II

2. Xe-II

3. He-II

4. Kr-II

20. The most suitable gas that can be used in experiments at absolute zero is

9. The method to isolate noble gases based on the boiling points uses 1. Claude’s apparatus

2. Clark’s apparatus

3. Kipp’s apparatus

4. None of the above

10. The type of bonds present in XeO4 are 1. Only σ bonds

2. Only π bonds

3. Both σ and π bonds

3. Vander Walls bonds

11. In clatharates the type of forces that exist between the host and guest are

NOBLE GASES

2. BeCl2

16. The credit of discovery of Noble gases goes to

1. CaCN2 and CO2

1. Ionic

1. SnCl2

2. Covalent

1. Helium

2. Argon

3. Krypton

4. Xenon

21. The maximum oxidation state that can be shown by Xe is 1. +6

2. +8

3. +4

4. +2

22. The most common Noble gas produced due to radioactive decay is 1. He

2. Ne

3. Xe

4. Rn

23. The noble gas, which is placed in wrong block is

©B.S.S.PRASAD

EAMCET CHEMISTRY

96

1. He

2. Ne

1. Ionisation energy

2. Atomic radius

3. Xe

4. Rn

3. Electron affinity

4. Both 2 and 3

24. The first chemical compound prepared by Bartlett is

33. radon does not form chemical compound, because of

1, XeF6

2. XeF4

1. Large size

3. XeF2

4. Xe(Pt)F6

3. High ionisation energy 4. Less half life

25. Fluorine and Oxygen from compounds with xenon but

2. Absence of d-orbtals

34. X is an element, with properties similar to Noble gases.

Nitrogen does not combine with Xenon , because

The atomic number of X could be

1.

It is an inert gas

1. 110

2. 112

2.

It has triple bond

3. 116

4. 118

3.

It is less electro negative

4.

It is small in size

26. The number of atoms present in one mole of helium are same as in

35. The type of π bond formed in XeO3 are 1. pπ-dπ

2. dπ-pπ

3. Both

4. None

36. The shape of XeF6 is

1.

One mole of Oxygen

1.

Otahedral

2.

28 grams of nitrogen

2.

Distorted octahedral

3.

1 gram of hydrogen

3.

Pentagonal bipyramidal

4.

22.4 L of Cl2 at STP

4.

Distorted pentagonal bipyramidal

27. Beacon lights and traffic signal lights use Noble gases ,

37. XeO4 is prepared by the

because

1.

Hydrolysis of XeF2

1.

They are very bright

2.

Hydrolysis of XeF4

2.

They consume less power

3.

Hydrolysis of XeF6

3.

They can diffuse through mist

4.

By reacting Na4XeO6 with concentrated H2SO4

4.

They are very colourful

28. If a mixture containing He, Ne, Ar and Kr are cooled by liquid Oxygen , Which one gets liquefied? 1. Only Kr

2. Only Kr and Ar

3. Only Kr, and Ne

4. All of them

29. Which of the following gives white precipitate with AgNO3?

38. The Noble gas used to detect the presence of π mesons is 1. He

2. Ne

3. Xe

4. Rn

39. The AB3 E2 type of compound is 1. XeF2

2. XeF4

3. XeF6

4. XeO3

40. The oxidation state of Xe in sodium perxenate is

1. XeF2

2. XeF4

1. +2

2. +4

3. XeF6

4. None

3 +6

4 +8

30. The mixture of gases that result after an electric arc is struck in a bulb containing pure air. Is passed into bubbler containing Caustic potash. The compound that forms is 1. NaNO3

2. KNO3

3. Na2CO3

4. None of the above

31. Which was called as lazy gas ? 1. He

2. Ne

3. Ar

4. Kr

32. Which of the following periodic properties does not keep to the trend across the period in case of Noble gases? NOBLE GASES

Key 1

2

9

1

17

4

25

3

33

4

2

3

10

3

18

4

26

3

34

4

3

1

11

3

19

3

27

3

35

2

4

1

12

2

20

1

28

1

36

2

5

1

13

4

21

2

29

4

37

4

6

2

14

1

22

1

30

2

38

2

7

3

15

2

23

1

31

3

39

2

8

3

16

2

24

4

32

4

40

4