# JEE Main > pBlock Elements

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

Physics
Chemistry
Maths

Q 1.

Correct4

Incorrect-1

Alum helps in purifying water by

A

forming Si complex with clay partiles

B

sulphate part which combines with the dirt and removes it

coagulaing the mud particles

D

making mud water soluble.

##### Explanation

Q 2.

Correct4

Incorrect-1

In {tex} \mathrm { XeF } _ { 2 } , \mathrm { XeF } _ { 4 } , \mathrm { XeF } _ { 6 } {/tex} the number of lone pairs on {tex} \mathrm { Xe } {/tex} are respectively

A

{tex} 2,3,1 {/tex}

B

{tex} 1,2,3 {/tex}

C

{tex} 4,1,2 {/tex}

{tex} 3,2,1 {/tex}

##### Explanation

Q 3.

Correct4

Incorrect-1

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

Q 4.

Correct4

Incorrect-1

Which of the following statements is true?

A

HF is less polar than HBr

B

absolutely pure water does not contain any ions

chemical bond formation take place when forces of attraction overcome the forces of repulsion

D

in covalency transference of electron takes place.

##### Explanation

Q 5.

Correct4

Incorrect-1

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

A

6

B

7

C

17

16

##### Explanation

Q 6.

Correct4

Incorrect-1

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

Q 7.

Correct4

Incorrect-1

What may be expected to happen when phosphine gas is mixed with chlorine gas?

A

{tex} \mathrm { PCl } _ { 3 } {/tex} and {tex} \mathrm { HCl } {/tex} are formed and the mixture warms up

B

{tex} \mathrm { PCl } _ { 5 } {/tex} and {tex} \mathrm {HCl} {/tex} are formed and the mixture cools down

C

{tex} \mathrm { PH } _ { 3 }. \mathrm { Cl } _ { 2 } {/tex} is formed with warming up

The mixture only cools down

##### Explanation

Q 8.

Correct4

Incorrect-1

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

Q 9.

Correct4

Incorrect-1

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

Q 10.

Correct4

Incorrect-1

Glass is a

super-cooled liquid

B

gel

C

polymeric mixture

D

micro-crystalline solid

##### Explanation

Q 11.

Correct4

Incorrect-1

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

Q 12.

Correct4

Incorrect-1

For making good quality mirrors, plates of float glass are used. These are obtained by floating molten glass over a liquid metal which does not solidify before glass. The metal used can be

A

tin

B

sodium

C

magnesium

mercury

##### Explanation

Q 13.

Correct4

Incorrect-1

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

Q 14.

Correct4

Incorrect-1

Which one of the following statement regarding helium is incorrect?

A

It is used to produce and sustain powerful superconducting magnets

B

It is used as a cryogenic agent for carrying out experiments at low temperatures

It is used to fill gas balloons instead of hydrogen because it is lighter and non-inflammable

D

It is used in gas-cooled nuclear reactors

##### Explanation

Q 15.

Correct4

Incorrect-1

Beyllium and aluminium exhibit many properties which are similar. But, the two elements differ in

A

forming covalent halides

B

forming polymeric hydrides

exhibiting maximum covalency in compounds

D

exhibiting amphoteric nature in their oxides

##### Explanation

Q 16.

Correct4

Incorrect-1

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

Q 17.

Correct4

Incorrect-1

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

Q 18.

Correct4

Incorrect-1

The number of hydrogen atom(s) attached to phosphorus atom in hypophosphous acid is

A

three

B

one

two

D

zero

##### Explanation

Q 19.

Correct4

Incorrect-1

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

Q 20.

Correct4

Incorrect-1

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

Q 21.

Correct4

Incorrect-1

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

Q 22.

Correct4

Incorrect-1

The structure of diborane {tex} \left( \mathrm { B } _ { 2 } \mathrm { H } _ { 6 } \right) {/tex} contains

A

four {tex} 2 \mathrm { c } - 2 \mathrm { e } {/tex} bonds and four {tex} 3 \mathrm { c } - 2 \mathrm { e } {/tex} bonds

B

two {tex} 2 \mathrm { c } - 2 \mathrm { e } {/tex} bonds and two {tex} 3 \mathrm { c } - 3 \mathrm { e } {/tex} bonds

C

two {tex} 2 \mathrm { c } - 2 \mathrm { e } {/tex} bonds and four {tex} 3 \mathrm { c } - 2 \mathrm { e } {/tex} bonds

four {tex} 2 \mathrm { c } - 2 \mathrm { e } {/tex} bonds and two {tex} 3 \mathrm { c } - 2 \mathrm { e } {/tex} bonds

##### Explanation

Q 23.

Correct4

Incorrect-1

Which of the following statements is true?

A

{tex} \mathrm { HClO } _ { 4 } {/tex} is a weaker acid than {tex} \mathrm { HClO } _ { 3 } {/tex}

{tex} \mathrm { HNO } _ { 3 } {/tex} is a stronger acid than {tex} \mathrm { HNO } _ { 2 } {/tex}

C

{tex} \mathrm { H } _ { 3 } \mathrm { PO } _ { 3 } {/tex} is a stronger acid than {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 3 } {/tex}

D

In aqueous medium {tex} \mathrm { HF} {/tex} is a stronger acid than {tex} \mathrm { HCl} {/tex}

##### Explanation

Q 24.

Correct4

Incorrect-1

The increasing order of the first ionization enthalpies of the elements {tex} \mathrm { B } , \mathrm { P } , \mathrm { S } {/tex} and {tex} \mathrm { F } {/tex} (Lowest first) is

A

{tex} \mathrm { B } < \mathrm { P } < \mathrm { S } < \mathrm { F } {/tex}

{tex} \mathrm { B } < \mathrm { S } < \mathrm { P } < \mathrm { F } {/tex}

C

{tex} \mathrm { F } < \mathrm { S } < \mathrm { P } < \mathrm { B } {/tex}

D

{tex} \mathrm { P } < \mathrm { S } < \mathrm { B } < \mathrm { F } {/tex}

##### Explanation

Q 25.

Correct4

Incorrect-1

What products are expected from the disproportionation reaction of hypochlorous acid?

A

{tex} \mathrm { HCl } {/tex} and {tex} \mathrm { Cl } _ { 2 } \mathrm { O } {/tex}

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

C

{tex} \mathrm { HClO } _ { 3 } {/tex} and {tex} \mathrm { Cl } _ { 2 } \mathrm { O } {/tex}

D

{tex} \mathrm { HClO } _ { 2 } {/tex} and {tex} \mathrm { HClO } _ { 4 } {/tex}