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Previous Year Questions Of Non-Metals and Their Compounds

Previous Year Questions Of Non-Metals and Their Compounds

Q 2744101053

Molecules of which of the following has
cage like structure ?
1. Diamond
2: Graphite
3. · Fullerenes
Select the correct answer using the code given below :
NDA Paper 2 2017
(A)

1, 2 and 3

(B)

2 and 3 only

(C)

2 only

(D)

3 only

Solution:

Correct Answer is `=>` (D) 3 only
Q 2764101055

Temporary hardness in water is due to which one of the following of Calcium and Magnesium ?
NDA Paper 2 2017
(A)

Hydrogencarbonates

(B)

Carbonates

(C)

Chlorides

(D)

Sulphates

Solution:

Correct Answer is `=>` (A) Hydrogencarbonates
Q 2744312253

Which one of the following elements forms highest number of compounds ?
NDA Paper 2 2017
(A)

Oxygen

(B)

Hydrogen

(C)

Chlorine

(D)

Carbon

Solution:

Correct Answer is `=>` (D) Carbon
Q 2149701613

Which one of the following oxides of nitrogen is known as 'anhydride' of nitric acid?
NDA Paper 2 2016
(A)

`N_(2)O`

(B)

`N_(2)O_(3)`

(C)

`NO_(2)`

(D)

`N_(2)O_(5)`

Solution:

`NO_(2)` is the anhydride of nitric acid.`NO_(2)` is used to

generate anhydrous metal nitrates from the oxides.

`MO + 3NO_(2) -> M(NO_(3) )_(2) + NO`
Correct Answer is `=>` (C) `NO_(2)`
Q 2119323210

Density of water is
NDA Paper 2 2016
(A)

maximum at `0 ^(0)C`

(B)

minimum at `0 ^(0)C`

(C)

maximum at `4 ^(0)C`

(D)

maximum at `-4 ^(0)C`

Solution:

Water shows anomalous behaviour between

temperatures `0 ^(0)C` and `4 ^(0)C`. Expands if temperature

goes below `4 ^(0)C`

Therefore, density decreases below `4 ^(0)C`. Also, it

expands when temperature goes above `4 ^(0)C`

Therefore, density of water is maximum at `4 ^(0)C`

because volume is minimum at `4 ^(0)C`
Correct Answer is `=>` (C) maximum at `4 ^(0)C`
Q 2139634512

Which of the following carbon compounds will not give a sooty flame ?
NDA Paper 2 2016
(A)

Benzene

(B)

Hexane

(C)

Naphthalene

(D)

Anthracene

Solution:

Hexane `(C_(6) H_(14) )` will not give a sooty flame. Hexane is a significant constituent of gasoline. The darker or sootier the smoke, the more unsaturated the compound. On the other hand if the flame is burning relatively clearer and clearer then the compound is saturated. Hexane burns with a clear and luminous flame.
Correct Answer is `=>` (B) Hexane
Q 1658656504

Permanent hardness of water is due to the presence of
NDA Paper 2 2015
(A)

sulphates of sodium and potassium

(B)

sulphates of magnesium and calcium

(C)

carbonates of sodium and magnesium

(D)

bicarbonates of magnesium and calcium

Solution:

Chlorides and sulphates of magnesium `(Mg)` and calcium `(Ca)` are responsible for the permanent hardness of water, as hardness due to them cannot be removed by just boiling. Note Biocarbonates of `Mg` and `Ca` lead to temporary hardness which can be removed by boiling.
Correct Answer is `=>` (B) sulphates of magnesium and calcium
Q 1740145013

A sample of gas is to be identified by means of its behavior in the presence of a glowing splint. Which of the following gases will neither itself burn nor cause the splint to burn?
NDA Paper 2 2014
(A)

Oxygen

(B)

Nitrogen

(C)

Hydrogen

(D)

Methane

Solution:

Nitrogen is an inert gas neither itself burn nor cause the splint to burn.
Correct Answer is `=>` (B) Nitrogen
Q 1762756635

Di-hydrogen can be prepared on a commercial scale by the action of steam on hydrocarbons, when a mixture of `CO` and `H_2` gas is formed. It is known as.
NDA Paper 2 2014
(A)

water gas

(B)

producer gas

(C)

industrial gas

(D)

fuel gas

Solution:

Nitrogen is an inert gas neither itself burn nor cause the splint to burn.
Correct Answer is `=>` (B) producer gas
Q 1772856736

Which of the following statements about hydrogen is/are correct?

1. Hydrogen has three isotopes of which protium is the most common.

2. Hydrogen ion `(H^+)` exists freely in solution.

3. Di-hydrogen `H_2`, acts as a reducing agent.

Select the correct answer using the codes given below
NDA Paper 2 2014
(A)

1, 2 and 3

(B)

Only 1

(C)

1 and 3

(D)

Only 3

Solution:

Nitrogen is an inert gas neither itself burn nor cause the splint to burn.
Correct Answer is `=>` (B) Only 1
Q 1752156934

Which of the following statements is correct?


NDA Paper 2 2014
(A)

Fullerenes have only six-membered carbon rings

(B)

Fullerenes are cage-like molecules

(C)

Diamond is thermodynamically the most stable allotrope of carbon

(D)

Graphite is slippery and hard and is therefore used as a dry lubricant in machines

Solution:

Nitrogen is an inert gas neither itself burn nor cause the splint to burn.
Correct Answer is `=>` (D) Graphite is slippery and hard and is therefore used as a dry lubricant in machines
Q 1722467331

The most stable form of carbon is
NDA Paper 2 2014
(A)

diamond

(B)

graphite

(C)

fullerene

(D)

coal

Solution:

The most stable form of carbon is diamond.
Correct Answer is `=>` (A) diamond
Q 2376180976

Oxygen on reaction with non-metals forms oxides, which are
NDA Paper 2 2013
(A)

basic oxides

(B)

acidic oxides

(C)

amphoteric oxides

(D)

neutral oxides

Solution:

Acidic oxides are oxides of either non-metals or of metals in high oxidation states. They are formed when a non-metal burns.
Correct Answer is `=>` (B) acidic oxides
Q 2357745684

The pure form of carbon is
NDA Paper 2 2013
(A)

diamond

(B)

graphite

(C)

charcoal

(D)

fullerene

Solution:

Diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centred cubic crystal structure called a diamond lattice. It has remarkable optical properties.
Correct Answer is `=>` (A) diamond
Q 2307745688

Which of the following statements in connection with the properties of water is /are correct?

1. Water has higher specific heat in comparison with other liquid.
2. Water has no dipole moment.
3. Water has low heat of vaporisation.
Select the correct answer using the codes given below
NDA Paper 2 2013
(A)

Only 1

(B)

2 and 3

(C)

1 and 3

(D)

Only 3

Solution:

Water has a very high specific heat capacity, the second highest among all the heteroatomic species (after ammonia), as well as a high heat of vaporisation, both of which are a result of the extensive hydrogen bonding between its molecules.
Correct Answer is `=>` (A) Only 1
Q 2347845783

Water is a good solvent. This is due to high
NDA Paper 2 2013
(A)

dielectric constant of water

(B)

surface tension of water

(C)

specific heat of water

(D)

heat of fusion of water

Solution:

A solvent is a substance that dissolves a solute (chemically different, liquid, solid or gas), resulting in a solution. Water is good solvent because it has very high dielectric constant of 76.6. A high dielectric constant means the molecule is very polar and have the ability to solvate/ stabilise ions better.
Correct Answer is `=>` (A) dielectric constant of water
Q 2377845786

Which of the following statements regarding the property of hard water is/are correct?
1. Temporary hardness of water is due to the presence of soluble magnesium and calcium hydrogen carbonate.
2. Temporary hardness of water can be removed by boiling.
3. Calgon's method is applied to remove temporary hardness of water.
4. Permanent hardness of water is removed by clark's method.

Select the correct answer using the codes given below
NDA Paper 2 2013
(A)

1 and 2

(B)

1, 2 and 3

(C)

3 and 4

(D)

Only 2

Solution:

Clark's method is used to remove temporary hardness from water on a large scale. Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate).
In Clark's method, a calculated amount of lime water `Ca(OH)_2` is added to tanks containing hard water. The bicarbonates of calcium and magnesium present in water are converted into soluble carbonates which settle down at the bottom and the soft water is drained off.

`M(HCO_3)_2 + Ca(OH)_2 underset(Method) overset(Clarke)(->) MCO_3 + CaCO_3 + H_2O`

(where M = Mg or Ca)
Correct Answer is `=>` (B) 1, 2 and 3
Q 2317045880

Statement I Hard water does not give lather with soap.
Statement II Calcium and magnesium salts present in hard water form precipitate with soap.
NDA Paper 2 2013
(A)

Both the statements are individually true and Statement II is the correct explanation of Statement I

(B)

Both the statements are individually true and Statement II is not the correct explanation of Statement I

(C)

Statement I is true, but Statement II is false

(D)

Statement I is false, but Statement II is true

Solution:

The hardness of water is mainly due to the presence of Ca or Mg ions. When hard water containing these ions is treated with soap solution, it reacts to form white curdy precipitate known as scum.


`underset (Soap\ \ solution)(2C_17 H_35 COONA) + Ca^(+2) -> underset(Scum)((C_17 H_35 COO)_2) Ca + 2Na`
Correct Answer is `=>` (A) Both the statements are individually true and Statement II is the correct explanation of Statement I
Q 2387456387

Deionised water is produced by
NDA Paper 2 2012
(A)

calgon process

(B)

ion-exchange resin process

(C)

Clark's process

(D)

permutit process

Solution:

Purified water is water that is mechanically filtered or
processed to be cleaned for consumption. Distilled water and
deionised (DI) water have been the most common forms of
purified water, but water can also be purified by other processes
including reverse osmosis, carbon filtration, microfiltration.
ultrafiltration, ultraviolet oxidation or electrodialysis.
Correct Answer is `=>` (B) ion-exchange resin process
Q 2377256186

Consider the following statements
1. Diamond is hard and graphite is soft.
2. Diamond is soft and graphite is hard.
3. Diamond is a bad conductor, but graphite is a good conductor.
4. Diamond is a good conductor, but graphite is a bad conductor.
Which of the statement(s) given above is/are correct?
NDA Paper 2 2012
(A)

1 and 3

(B)

Only 1

(C)

2 and 3

(D)

1 and 4

Solution:

Diamond and graphite are two allotropes of carbon pure forms of the same element that differ in structure. Diamond is hard and graphite is soft whereas diamond is bad conductor but graphite is a good conductor. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is renowned as a. material with superlative physical qualities, most of which onginate from the strong covalent bonding between its atoms.
Correct Answer is `=>` (A) 1 and 3
Q 2317056880

A glass of water does not turn into ice as it reaches `0^o C`. It is because
NDA Paper 2 2012
(A)

water does not solidify at `0^o C`

(B)

a certain arnount of heat must be supplied to the glass of water so as to solidify

(C)

a certain amount of heat must be taken out from the glass of water so as to solidify

(D)

Only water solidifies at 0 K

Solution:

Water does not actually freeze when it reaches `0^o C`, because it requires the removal of the 'heat of fusion' (enthalpy-internal energy) to change phase. Water will cool slightly below `0^o` and remain at that temperature uatil it has fully crystallised into ice.
Correct Answer is `=>` (C) a certain amount of heat must be taken out from the glass of water so as to solidify
Q 2317178980

Which of the statements given below is/are correct?
Permanent hardness of water is due to the presence of soluble
1. chloride of calcium
2. bicarbonate of calcium
3. sulphate of magnesium
4. bicarbonate of magnesium
Select the correct answer using the codes given below.
NDA Paper 2 2011
(A)

Only 1

(B)

1 and 3

(C)

2 and 4

(D)

1, 2 and 3

Solution:

Chlorides and sulphates of calcium and magnesium are responsible for permanent hardness of water. Permanent hardness can't be removed by boiling. It can be removed by washing soda, permutit. synthetic resin and calgon.

Note : Bicarbonates of magnesium and calcium are responsible for temporary hardness of water.
Correct Answer is `=>` (B) 1 and 3
Q 2377178986

Which of the following statements about diamond are correct'?
l. It is used as a gem in jewellery because of its ability to reflect light.
2. It is a good conductor of electricity.
3. It is used for cutting glass, marble stones and other hard materials.
4. It is used for drilling of rocks.
Select the correct answer using the codes given below.
NDA Paper 2 2011
(A)

1, 3 and 4

(B)

2, 3 and 4

(C)

1, 2 and 3

(D)

2 and 4

Solution:

Diamond, an allotrope of carbon, has high refractive and reflective powers because of which it is used as a gem in jewellery. It is used for cutting glass. marble stones and other hard materials and for drilling of rocks. It is a bad conductor of electricity because all the electrons are used in bond formation and there is no mobile electron in the system. It is the hardest material known.
Correct Answer is `=>` (A) 1, 3 and 4
Q 2387178987

Which one among the following methods is not effective in removing arsenic from contaminated ground water?
NDA Paper 2 2011
(A)

Boiling

(B)

Reverse osmosis

(C)

ion exchange

(D)

Coagulation adsorption

Solution:

Osmosis or electrodialysis (rnembrane filter), ion exchange (through suitable cation and anion exchange), coagulation adsorption etc, are used to remove arsenic from contaminated ground water. Thus, boiling is not effective in removing arsenic from contaminated ground water.
Correct Answer is `=>` (A) Boiling
Q 2337380282

A student heated some sulphur in a spatula and collected the gas X. Which one among the following is correct about X?
NDA Paper 2 2011
(A)

X is `SO_2` and it turns moist litmus to blue

(B)

X is `SO_3` and it turns moist litmus to blue

(C)

X is `SO_2` and it turns moist litmus to red

(D)

X is `SO_3` and it turns dry litmus to blue

Solution:

Sulphur burns in air forming mainly sulphur dioxide.

`S + O_2 -> SO_2`
`SO_2` is an acidic gas, thus it turns moist litmus to red.
Correct Answer is `=>` (C) X is `SO_2` and it turns moist litmus to red
Q 2367380285

When concentrated `H_2SO_4` splits on the surface, it should be immediately cleaned
NDA Paper 2 2011
(A)

with a piece of cloth

(B)

by adding cold water

(C)

by adding solid `Na_2CO_3`

(D)

by adding solid `BaCl_2`

Solution:

When concentrated `H_2SO_4` splits on the surface, it should be immediately cleaned by adding solid `BaCl_2` because `BaCl_2` forms solid `BaSO_4` and HCI.

`H_2SO_4 + BaCl_2 -> underset(White\ \ppt.)(BaSO_4) ↓ + 2HCl`
Correct Answer is `=>` (D) by adding solid `BaCl_2`
Q 2317391289

Consider the following statements with regard to the properties of water.
1. Water is a good solvent for ionic compounds but poor solvent for covalent compounds.
2. Water is a good solvent for covalent compounds but poor solvent for ionic compounds.
3. Water has maximum density at the temperature 277 K.
Which of the statements given above are correct?
NDA Paper 2 2010
(A)

1 and 3

(B)

2 and 3

(C)

1 and 2

(D)

1, 2 and 3

Solution:

Ionic solids are soluble in polar solvents like water but covalent molecules are not because like dissolves like. Water has maximum density at `4^oC` or `277 K`. Above or below this temperature the density will decrease.
Correct Answer is `=>` (A) 1 and 3
Q 2358312204

Which one among the following statements is not correct about graphite'?
NDA Paper 2 2010
(A)

It is the most stable allotrope of carbon

(B)

It is an electrically conducting material

(C)

Crystalline spherical beads of graphite have very good lubricating property under dry conditions

(D)

It is the higher grade of coal

Solution:

Graphite is thermodynamically most stable crystalline allotrope of carbon. It is a good conductor of electricity due to presence of free p-electrons (`pi`-electrons) and can be used as a good lubricant in dry conditions.
Correct Answer is `=>` (D) It is the higher grade of coal
Q 2358112904

Match the following






Column IColumn II
(A) Ozone gas(1) Combines with haemoglobin
(B) Nitrous oxide(2) Ultraviolet radiation
(C) Carbon dioxide (3)Component of air in small
quantity
(D) Carbon monoxide (4) Visible radiation
(5) Infrared radiation

NDA Paper 2 2010
(A)

`A-> 3, quad B-> 4, quad C->1, quad D->2`

(B)

`A-> 2, quad B-> 3, quad C->5, quad D->1`

(C)

`A-> 2, quad B-> 3, quad C->4, quad D->5`

(D)

`A-> 4, quad B-> 1, quad C->2, quad D->3`

Solution:

Ozone gas is impermeable for ultraviolet radiations, thus protects us from harmful UV radiations coming from the Sun. Nitrous oxide is present in small quantity (0.5 ppm) in air. Carbon dioxide does not allow infrared radiations to pass through it and thus, it maintains the temperature of the Earth. Carbon monoxide combines more readily with haemoglobin as compared to oxygen and thus, reduces its oxygen carrier capacity.
Correct Answer is `=>` (B) `A-> 2, quad B-> 3, quad C->5, quad D->1`
Q 2317323280

Dry ice is used for making cold-baths in laboratories by mixing with volatile organic solvents. Identify the form of dry ice from the following.
NDA Paper 2 2009
(A)

Gaseous carbon dioxide

(B)

Liquid carbon dioxide

(C)

Solid carbon dioxide

(D)

Solid hydrogen oxide

Solution:

Solid carbon dioxide is technically known as dry ice (drikold). It is used for making cold-l) maths in laboratories by mixing with' volatile organic solvents It produces very low temperature (`-100°C`) with ether and hence, gives an excellent freezing mixture.
Correct Answer is `=>` (C) Solid carbon dioxide
Q 2367323285

Following statements are made in connection with carbon dioxide (`CO_2` )
l. `CO_2` is a poisonous gas.
2. `CO_2` is an acidic oxide.
3. `CO_2` turns lime water milky.
Which if the statements given above is/are correct?
NDA Paper 2 2009
(A)

1 and 2

(B)

2 and 3

(C)

Only 3

(D)

1 and 3

Solution:

Carbon dioxide is a non-poisonous gas. It is an acidic
oxide because it dissolves in water to give carbonic acid `(H_2CO_3 )`.

`CO_2+underset(pH=7)(H_2O)-> underset(text(carbonic acid)(pH < 7))(H_2CO_3)`

Carbon dioxide (`CO_2`) turns lime water milky due to the formation
of calcium carbonate.

`underset(text(Lime water))(Ca(OH)_2)+CO_2(g)->underset(text(Calcium carbonate))(CaCO_3) downarrow +H_2O`
Correct Answer is `=>` (B) 2 and 3
Q 2337523482

Diamond is a
NDA Paper 2 2009
(A)

good conductor and soft

(B)

non-conductor and soft

(C)

non-conductor and hard

(D)

good conductor and hard

Solution:

In diamond, all the electrons are used in bond
formation and lherefore, there is no mobile electron in the
system. Hence, diamond is a non-conductor of electricity.
In diamond, atoms are held together by very strong covalent
bonds which results in three dimensional network structure and
therefore, diamond is the hardest substance known
Correct Answer is `=>` (C) non-conductor and hard
Q 2367534485


NDA Paper 2 2009

Assertion : Carbon can form more compounds than any other element.

Reason : Carbon can exist in various allotropes.

(A) Both A and R individually true and R is the correct explanation of A
(B) Both A and R are individually true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
Solution:

Since, carbon-carbon bond strength is very high due
to small size of carbon, it has maximum tendency of catenation,
(i.e., has a higher tendency of self-linking to form long chain or
rings). That's why carbon can form more compounds than any
other element known.
Carbon can exist in various allotropic forms.
Crystalline allotropes- Diamond, graphite, fullerence
Amorphous allotropes- Coal, coke, charcoal etc.
Correct Answer is `=>` (B)
Q 2317534489

Alum is used as
NDA Paper 2 2009
(A)

an analgesic

(B)

a fertilizer

(C)

a disinfectant

(D)

a purifier for water

Solution:

Alum `[K _2SO_4 * Al_ 2(SO _4)_3 *24 H_2O]` causes coagulation
of mud particles, hence it iG used for water purification. It also has
antiseptic properties.
Correct Answer is `=>` (D) a purifier for water
Q 2337634582

Oxygen and ozone are
NDA Paper 2 2009
(A)

allotropes

(B)

isomers

(C)

isotopes

(D)

isobars

Solution:

Allotropism is also caused by the presence of different
number of atoms. Hence, oxygen `(O_2)` and ozone, `(O_3 )` are two
allotropes of oxygen.
Correct Answer is `=>` (A) allotropes
Q 2337145082

Consider the following statements regarding diamond.
1. It is an allotrope of silicon.
2. It is a bad conductor of electricity.
3. It is the hardest substance.
4. It burns to produce carbon dioxide.
Which of the statements given above are correct?
NDA Paper 2 2009
(A)

1, 2, 3 and 4

(B)

2, 3 and 4

(C)

1 and 2

(D)

1, 3 and 4

Solution:

Diamond is an allotrope of carbon, not silicon.It is bad conductor of electricity because all the electrons are used in bond formation and there is no mobile electron in the system. In diamond carbon atoms are linked by strong covenant bonds and form three dimensional polymeric structure. Due to this reason diamond is the hardest substance. On burning in air or oxygen, it forms carbon dioxide.
Correct Answer is `=>` (B) 2, 3 and 4
Q 2317745689

Each of the given items
consist of t:wo statements, one labelled as the 'Assertion (A)'
and the other as 'Reason (R)'. You are to examine these two
statements carefully and select the answers to these items
using the codes given below.
NDA Paper 2 2008

Assertion : Diamond is a good conductor of electricity.

Reason : Diamond and graphite are two allotrope of carbon and graphite is a good conductor of electricity.

(A) Both A and R individually true and R is the correct explanation of A
(B) Both A and R are individually true but R is not the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true
Solution:

Diamond and graphite both are the allotropes of
carbon. Graphite has `sp^2` hybridised C atoms, thus also has a
delocalised `pi`-electron cloud. Due to the presence of this
electron cloud, graphite is a good conductor of electricity. While
in diamond, C-atoms are `sp^3` hybridised, and all the electrons are
used in bond formation, hence no valence electron is available.
Therefore, it is a bad conductor of electricity.
Correct Answer is `=>` (D)
Q 2387056887

Which of the following statements regarding carbon dioxide is/are correct ?
l. It is prepared on large scale by the action of water on lime.
2. In the solid form, it can be used as a refrigerant.
Select the correct answer using the codes given below.
NDA Paper 2 2008
(A)

Only 1

(B)

Only 2

(C)

Both 1 and 2

(D)

Neither 1 nor 2

Solution:

On large scale, `CO_2` is prepared by heating limestone
in lime kilns.

`underset(text(Limestone))(CaCO_3)-> underset(text(Lime))(CaO)+CO_2 uparrow`

While lime on reaction with water gives milk of lime, not `CO_ 2`

`underset(text(Lime))(CaO)+H_2O-> underset(text(Milk of lime))(Ca(OH)_2) downarrow`

`CO_2` in solid form is called dry ice or drikold and used as a
refrigerant (coolant) because it produces very low temperature
as compared to common ice.
Correct Answer is `=>` (B) Only 2
Q 2347167083

Which one of the following materials is suitable for water purification?
NDA Paper 2 2008
(A)

Silicones

(B)

Zeolites

(C)

Asbestos

(D)

Quartz

Solution:

Zeolites are used to purify water. They combine with
calcium and magnesium ions of hard water and form calcium and
magnesium salts of permuit (zeolite) which can be easily removed.

`underset(text(sodium zeolite))(Na_2Z)
+underset(text(Calcium sulphate {from hard water))(CaSO_4)
-> underset(text(Calcium zeolite))(CaZ)+Na_2SO_4`

`Na_2Z+underset(text(From hard water))(MgSO_4)
-> underset(text(Magnesium zeolite))(MgZ)+Na_2SO_4`
Correct Answer is `=>` (C) Asbestos
Q 2387567487

Which one of the following is the most important characteristic of water to act as a good solvent?
NDA Paper 2 2008
(A)

Purity of water

(B)

Ionising power of water

(C)

Polar nature of water

(D)

Dissolving power of water

Solution:

The polar natum of water makes it an excellent solvent for many other polar and ionic substances. Due to its polar nature. it has high dielectric constant and therefore, has the ability to dissolve most of the inorganic (ionic) compounds and thus is regarded as a universal solvent.
Correct Answer is `=>` (C) Polar nature of water
Q 2347178083

Which one of the following is not an allotrope of carbon?
NDA Paper 2 2007
(A)

Soot

(B)

Graphite

(C)

Diamond

(D)

Carborundum

Solution:

Carborundum (`SiC`) is also known as silicon carbide. It is not an allotrope of carbon. While diamond and graphite are crystalline allotropes and soot is amorphous allotrope of carbon.
Correct Answer is `=>` (D) Carborundum
Q 2317478389

Why is nitrogen molecule chemically less active?
NDA Paper 2 2007
(A)

It has small atomic radius

(B)

It has high electronegativity

(C)

It has high dissociation energy

(D)

It has stable electronic configuration

Solution:

Nitrogen is a colorless gas and exists as diatomic molecule. The two nitrogen atoms are held together by triple bond and have very high bond dissociation energy (`945` `kJ mol^(-1)`). Hence, due to the presence of triple bond which has very high bond dissociation energy, the nitrogen molecule is chemically less active.

`:Nequiv equiv N:`
Correct Answer is `=>` (C) It has high dissociation energy
Q 2387778687

Yellow colour of usual nitric acid is due to the presence of which one of the following?
NDA Paper 2 2007
(A)

`N_2O`

(B)

`NO`

(C)

`N_2O_5`

(D)

`NO_2`

Solution:

The yellow colour of usual nitric acid is due to the
presence of nitrogen dioxide, `NO_2` (formed by the decomposition
of `HNO_3` in sunlight) in it.

`4HNO_3 underset(text(or heat))overset(text(Sunlight))-> 4NO_2+2H_2O+O_2`
Correct Answer is `=>` (D) `NO_2`
Q 2317680589

Which one of the following is the correct statement about graphite?
NDA Paper 2 2007
(A)

A rigid structure

(B)

Low viscosity

(C)

Layered structure

(D)

Low melting point

Solution:

Graphite has a two dimensional sheet like structure. The adjacent layers of sheet are held together by weak van der Waals' forces. Due to wide separation and weak van der Waals' forces, the two adjacent layers can easily slide over each other, hence graphite is soft, greasy and has a lubricant character.
Correct Answer is `=>` (C) Layered structure
Q 2307780688

Which one of the following is the correct statement about graphite?
NDA Paper 2 2007
(A)

A rigid structure

(B)

Low viscosity

(C)

Layered structure

(D)

Low melting point

Solution:

Graphite has a two dimensional sheet like structure. The adjacent layers of sheet are held together by weak van der Waals' forces. Due to wide separation and weak van der Waals' forces, the two adjacent layers can easily slide over each other, hence graphite is soft, greasy and has a lubricant character.
Correct Answer is `=>` (C) Layered structure
 
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