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JEE Main

Explore popular questions from pBlock Elements for JEE Main. This collection covers pBlock Elements previous year JEE Main questions hand picked by experienced teachers.

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Q 1. Ammonia reacts with excess of chlorine to form:

A

{tex} \mathrm { NH } _ { 3 } {/tex} and {tex} \mathrm { N } _ { 2 } {/tex}

{tex} \mathrm { NCl } _ { 3 } {/tex} and {tex} \mathrm { HCl } {/tex}

C

{tex} \mathrm { NCl } _ { 3 } {/tex} and {tex} \mathrm { N } _ { 2 } {/tex}

D

{tex} \mathrm { NH } _ { 4 } \mathrm { Cl } {/tex} and {tex} \mathrm { N } _ { 2 } {/tex}

Explanation

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Q 2. Amorphous boron is extracted from borax by following steps:
Borax{tex} \stackrel { ( x ) } { \longrightarrow } \mathrm { H } _ { 3 } \mathrm { BO } _ { 3 } \stackrel { \Delta } { \longrightarrow } \mathrm { B } _ { 2 } \mathrm { O } _ { 3 } \stackrel { ( \mathrm { Y } ) } { \longrightarrow } _ { \text {Boron } } {/tex}
Then {tex} \mathrm { X } {/tex} and {tex} \mathrm { Y } {/tex} are:

{tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } , \mathrm { Mg } {/tex}

B

{tex} \mathrm { HCl } , \mathrm { C } {/tex}

C

{tex} \mathrm { HCl } , \mathrm { Fe } {/tex}

D

{tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } , \mathrm { Al } {/tex}

Explanation

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Q 3. Which one of the following properties is not shown by NO?

A

It combines with oxygen to from nitrogen dioxide.

B

It's bond order is 2.5

It is diamagnetic in gaseous state.

D

It is a neutral oxide.

Explanation

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Q 4. The number of lone pairs, and the number of {tex} \mathrm { S } - \mathrm { S } {/tex} bonds in {tex} \mathrm { S } _ { 8 } {/tex} molecules are respectively:

A

8,8

16,8

C

8,16

D

{tex} 8,4 {/tex}

Explanation

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Q 5. The correct order of the thermal stability of hydrogen halides {tex} ( \mathrm { H } - \mathrm { X } ) {/tex} is

A

{tex} \mathrm { HI } > \mathrm { HCl } < \mathrm { HF } > \mathrm { HBr } {/tex}

B

{tex} \mathrm { HCI } < \mathrm { HF } > \mathrm { HBr } < \mathrm { HI } {/tex}

{tex} \mathrm { HF } > \mathrm { HCl } < \mathrm { HBr } > \mathrm { HI } {/tex}

D

{tex} \mathrm { HI } < \mathrm { HBr } > \mathrm { HCl } < \mathrm { HF } {/tex}

Explanation



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Q 6. Concentrated hydrochloric acid when kept in open air sometimes produces a cloud of white fumes. The explanation for it is that

oxygen in air reacts with the emitted HCl gas to form a cloud of chlorine gas

B

strong affinity of HCl gas for moisture in air results in forming of droplets of liquid solution which appears like a cloudy smoke.

C

due to strong affinity for water, concentrated hydrochloric acid pulls moisture of air towards itself. This moisture forms droplets of water and hence the cloud.

D

concentrated hydrochloric acid emits strongly smelling HCl gas all the time.

Explanation

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Q 7. Excess of {tex} \mathrm {KI } {/tex} reacts with {tex} \mathrm { CuSO } _ { 4 } {/tex}, solution and then {tex} \mathrm { Na } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 3 } {/tex} solution is added to it. Which of the statements is incorrect for this reaction?

A

{tex} \mathrm { Na } _ { 2 } \mathrm { S } _ { 2 } \mathrm { O } _ { 3 } {/tex} is oxidised

{tex} \mathrm { Cul } _ { 2 } {/tex} is formed

C

{tex} \mathrm { Cu } _ { 2 } \mathrm { I } _ { 2 } {/tex} is formed

D

Evolved {tex} \mathrm { I } _ { 2 } {/tex} is reduced

Explanation

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Q 8. The molecule having smallest bond angle is:

A

{tex} \mathrm { NCl } _ { 3 } {/tex}

B

{tex} \mathrm { AsCl } _ { 3 } {/tex}

{tex} \mathrm { SbCl } _ { 3 } {/tex}

D

{tex} \mathrm { PCl } _ { 3 } {/tex}

Explanation

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Q 9. Boron cannot form which one of the following anions?

{tex} \mathrm { BF } _ { 6 } ^ { 3 - } {/tex}

B

{tex} \mathrm { BH } _ { 4 } ^ { - } {/tex}

C

{tex} \mathrm { B } ( \mathrm { OH } ) ^ { - }_4 {/tex}

D

{tex} \mathrm { BO } _ { 2 } ^ { - } {/tex}

Explanation

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Q 10. Aluminium chloride exists as dimer, {tex} \mathrm { Al } _ { 2 } \mathrm { Cl } _ { 6 } {/tex} in solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives

A

{tex} \left[ \mathrm { Al } ( \mathrm { OH } ) _ { 6 } \right] ^ { 3 - } + 3 \mathrm { HCl } {/tex}

{tex} \left[ \mathrm { Al } \left( \mathrm { H } _ { 2 } \mathrm { O } \right) _ { 6 } \right] ^ { 3 + } + 3 \mathrm { Cl } ^ { - } {/tex}

C

{tex} \mathrm { Al } ^ { 3 + } + 3 \mathrm { Cl } ^ { - } {/tex}

D

{tex} \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } + 6 \mathrm { HCl } {/tex}

Explanation

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Q 11. Glass is a

super-cooled liquid

B

gel

C

polymeric mixture

D

micro-crystalline solid

Explanation

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Q 12. Which one of the following substances has the highest proton affinity?

A

{tex} \mathrm { H } _ { 2 } \mathrm { S } {/tex}

{tex} \mathrm { NH } _ { 3 } {/tex}

C

{tex} \mathrm { PH } _ { 3 } {/tex}

D

{tex} \mathrm { H } _ { 2 } \mathrm { O } {/tex}

Explanation

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Q 13. Which of the following statement is wrong?

The stability of hydride increases from {tex} \mathrm { NH } _ { 3 } {/tex} to {tex} \mathrm { BiH } _ { 3 } {/tex} in group 15 of the periodic table.

B

Nitrogen cannot form {tex} \mathrm { d } \pi - \mathrm { p } \pi {/tex} bond.

C

Single {tex} \mathrm { N } - \mathrm { N } {/tex} bond is weaker than the single {tex} \mathrm { P } - \mathrm { P } {/tex} bond

D

{tex} \mathrm { N } _ { 2 } \mathrm { O } _ { 4 } {/tex} has two resonance structures.

Explanation

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Q 14. In case of nitrogen, {tex} \mathrm { NCl } _ { 3 } {/tex} is possible but not {tex} \mathrm { NCl } _ { 5 } {/tex} while in case of phosphorous, {tex} \mathrm { PCl } _ { 3 } {/tex} as well as {tex} \mathrm { PCl } _ { 5 } {/tex} are possible. It is due to

availability of vacant {tex} d {/tex} orbitals in {tex} \mathrm { P } {/tex} but not in {tex} \mathrm { N } {/tex}

B

lower electronegativity of {tex} \mathrm { P } {/tex} than {tex} \mathrm { N } {/tex}

C

lower tendency of H-bond formation in {tex} \mathrm { P } {/tex} than {tex} \mathrm { N } {/tex}

D

occurrence of {tex} \mathrm { P } {/tex} in solid while {tex} \mathrm N {/tex} in gaseous state at room temperature.

Explanation

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Q 15. Number of sigma bonds in {tex} \mathrm { P } _ { 4 } \mathrm { O } _ { 10 } {/tex} is

A

6

B

7

C

17

16

Explanation

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Q 16. Which among the following factors is the most important in making fluorine the strongest oxidizing halogen?

A

Hydration enthalpy

B

lonization enthalpy

C

Electron affinity

Bond dissociation energy

Explanation

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Q 17. Heating an aqueous solution of aluminium chloride to dryness will give

A

{tex} \mathrm { Al } ( \mathrm { OH } ) \mathrm { Cl } _ { 2 } {/tex}

{tex} \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } {/tex}

C

{tex} \mathrm { Al } _ { 2 } \mathrm { Cl } _ { 6 } {/tex}

D

{tex} \mathrm { AlCl } _ { 3 } {/tex}

Explanation

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Q 18. Which one of the following reactions of xenon compounds is not feasible?

A

{tex} 3 \mathrm { XeF } _ { 4 } + 6 \mathrm { H } _ { 2 } \mathrm { O } \longrightarrow 2 \mathrm { Xe } + \mathrm { XeO } _ { 3 } + 12 \mathrm { HF } + 1.5 \mathrm { O } _ { 2 } {/tex}

B

{tex} 2 \mathrm { XeF } _ { 2 } + 2 \mathrm { H } _ { 2 } \mathrm { O } \longrightarrow 2 \mathrm { Xe } + 4 \mathrm { HF } + \mathrm { O } _ { 2 } {/tex}

C

{tex} \mathrm { Xe } \mathrm { F } _ { 6 } + \mathrm { RbF } \longrightarrow \mathrm { Rb } \left[ \mathrm { XeF } _ { 7 } \right] {/tex}

{tex} \mathrm { XeO } _ { 3 } + 6 \mathrm { HF } \longrightarrow \mathrm { XeF } _ { 6 } + 3 \mathrm { H } _ { 2 } \mathrm { O } {/tex}

Explanation

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Q 19. Graphite is a soft solid lubricant extremely difficult to melt The reason for this anomalous behaviour is that graphite

A

is an allotropic form of diamond

B

has molecules of variable molecular masses like polymers

has carbon atoms arranged in large plates of rings of strongly bound carbon atoms with weak interplate bonds

D

is a non-crystalline substance

Explanation


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Q 20. Which one of the following is the correct statement?

A

Boric acid is a protonic acid

B

Beryllium exhibits coordination number of six

Chlorides of both beryllium and aluminium have bridged chloride structures in solid phase

D

{tex} \mathrm { B } _ { 2 } \mathrm { H } _ { 6 } \cdot 2 \mathrm { NH } _ { 3 } {/tex} is known as 'inorganic benzene'

Explanation


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Q 21. The correct statement for the molecule, {tex} \mathrm { CsI } _ { 3 } {/tex} is:

A

It is a covalent molecule.

It contains {tex} \mathrm { Cs } ^ { + } {/tex} and {tex} \mathrm { I } _ { 3 } ^ { - } {/tex} ions.

C

It contains {tex} \mathrm { Cs } ^ { 3 + } {/tex} and {tex} \mathrm { I } ^ { - } {/tex} ions.

D

It contains {tex} \mathrm { Cs } ^ { + } , \mathrm { I } ^ { - } {/tex} and lattice {tex} \mathrm { I } _ { 2 } {/tex} molecule.

Explanation

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Q 22. Oxidation number of {tex} \mathrm {Cl} {/tex} in {tex} \mathrm {C a O Cl_2} {/tex} , (bleaching power) is:

A

zero, since it contains {tex} \mathrm { Cl } _ { 2 } {/tex}

B

{tex} - 1 , {/tex} since it contains {tex} \mathrm { Cl } ^ { - } {/tex}

C

{tex} + 1 , {/tex} since it contains {tex} \mathrm { ClO } ^ { - } {/tex}

{tex} + 1 {/tex} and {tex} - 1 {/tex} since it contains {tex} \mathrm { ClO } ^ { - } {/tex} and {tex} \mathrm { Cl } ^ { - } {/tex}

Explanation

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Q 23. Identify the incorrect statement among the following.

A

{tex} \mathrm { Br } _ { 2 } {/tex} reacts with hot and strong {tex} \mathrm { NaOH } {/tex} solution to give {tex} \mathrm { NaBr } {/tex} and {tex} \mathrm { H } _ { 2 } \mathrm { O } {/tex} .

B

Ozone reacts with {tex} \mathrm { SO } _ { 2 } {/tex} to give {tex} \mathrm { SO } _ {3} {/tex}

C

Silicon reacts with {tex} \mathrm { NaOH } _ { \mathrm {(aq)} } {/tex} in the presence of air to give {tex} \mathrm { Na } _ { 2 } \mathrm { SiO } _ { 3 } {/tex} and {tex} \mathrm { H } _ { 2 } \mathrm { O } {/tex} .

{tex} \mathrm {Cl_2}{/tex} reacts with excess of {tex} \mathrm {NH_3}{/tex} to give {tex}\mathrm { N _ { 2 } }{/tex} and {tex} \mathrm {H Cl } {/tex}.

Explanation

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Q 24. In silicon dioxide

A

there are double bonds between silicon and oxygen atoms

B

silicon atom is bonded to two oxygen atoms

C

each silicon atom is surrounded by two oxygen atoms and each oxygen atom is bonded to two silicon atoms

each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bonded to two silicon atoms.

Explanation


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Q 25. The reaction of zinc with dilute and concentrated nitric acid, respectively, produces:

A

{tex} \mathrm { NO } {/tex} and {tex} \mathrm { N } _ { 2 } \mathrm { O } {/tex}

B

{tex} \mathrm { NO } _ { 2 } {/tex} and {tex} \mathrm { N } _ { 2 } \mathrm { O } {/tex}

{tex} \mathrm { N } _ { 2 } \mathrm { O } {/tex} and {tex} \mathrm { NO } _ { 2 } {/tex}

D

{tex} \mathrm { NO } _ { 2 } {/tex} and {tex} \mathrm { NO } {/tex}

Explanation