p-Block Elements — Page 13 | JEE Chemistry

Q121

A. Ammonium salts produce haze in atmosphere. B. Ozone gets produced when atmospheric oxygen reacts with chlorine radicals. C. Polychlorinated biphenyls act as cleansing solvents. D. 'Blue baby' syndrome occurs due to the presence of excess of sulphate ions in water. Choose the correct answer from the options given below :

A B and C only

B A and D only

C A, B and C only

D A and C only

Correct Answer

Option D

Solution

Ammonium salts produce haze in atmosphere.

Ozone is produced when atmospheric oxygen reacts with oxygen atoms and not chlorine atoms.

Polychlorinated biphenyls have number of applications including their use as cleansing solvents.

‘Blue baby’ syndrome occurs due to the presence of excess of nitrate ions and not sulphate ions in water.

Q122

Potassium dichromate acts as a strong oxidizing agent in acidic solution. During this process, the oxidation state changes from :

A + 2 to + 1

B + 6 to + 2

C + 6 to + 3

D + 3 to + 1

Correct Answer

Option C

Solution

$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ acts as a strong oxidising agent in acidic medium.

During this process, oxidation state of $\mathrm{Cr}$ changes from $+6$ to $+3$ .

\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O}

Q123

Reaction of thionyl chloride with white phosphorus forms a compound [A], which on hydrolysis gives [B], a dibasic acid. [A] and [B] are respectively :

A P

_4

O

_6

and H

_3

PO

_3

B POCl

_3

and H

_3

PO

_4

C PCl

_5

and H

_3

PO

_4

D PCl

_3

and H

_3

PO

_3

Correct Answer

Option D

Solution

\begin{aligned} & \mathrm{P}_4+8 \mathrm{SOCl}_2 \rightarrow \underset{[\mathrm{A}]}{4 \mathrm{PCl}_3}+4 \mathrm{SO}_2+2 \mathrm{~S}_2 \mathrm{Cl}_2 \\\\ & \mathrm{PCl}_3+3 \mathrm{H}_2 \mathrm{O} \rightarrow \underset{[B]}{\mathrm{H}_3 \mathrm{PO}_3}+3 \mathrm{HCl} \end{aligned}

Q124

Compound A reacts with NH

_4

Cl and forms a compound B. Compound B reacts with H

_2

O and excess of CO

_2

to form compound C which on passing through or reaction with saturated NaCl solution forms sodium hydrogen carbonate. Compound A, B and C, are respectively :

A

\mathrm{Ca{(OH)_2},NH_4^ \oplus ,{(N{H_4})_2}C{O_3}}

B

\mathrm{CaC{l_2},NH_4^ \oplus ,{(N{H_4})_2}C{O_3}}

C

\mathrm{CaC{l_2},N{H_3},N{H_4}HC{O_3}}

D

\mathrm{Ca{(OH)_2},N{H_3},N{H_4}HC{O_3}}

Correct Answer

Option D

Solution

$\underset{(B)}{\mathrm{Ca}(\mathrm{OH})_{2}}+\mathrm{NH}_{4} \mathrm{Cl} \longrightarrow \mathrm{CaCl}_{2}+\underset{(B)}{\mathrm{NH}_{3}}+\mathrm{H}_{2} \mathrm{O}$

\begin{aligned} & \mathrm{NH}_{3}+\mathrm{H}_{2} \mathrm{O}+\underset{\text{ Excess }}{\mathrm{CO}_{2}} \longrightarrow \underset{(C)}{\mathrm{NH}_{4} \mathrm{HCO}_{3}} \\\\ & \mathrm{NH}_{4} \mathrm{HCO}_{3}+\mathrm{NaCl} \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}+\mathrm{NaHCO}_{3} \end{aligned}

Q125

\mathrm{K_2Cr_2O_7}

paper acidified with dilute

\mathrm{H_2SO_4}

turns green when exposed to :

A Sulphur dioxide

B Sulphur trioxide

C Hydrogen sulphide

D Carbon dioxide

Correct Answer

Option A

Solution

$\mathrm{SO}_{2}$ gets oxidised in presence of $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ and it converts to $\mathrm{Cr}^{+3}$ in presence of dil.

$\mathrm{H}_{2} \mathrm{SO}_{4}$ .

Similarly, $\mathrm{H}_{2} \mathrm{~S}$ can also get oxidized to sulphur.

However, most appropriate is (A) Sulphur dioxide.

Q126

Which of the Phosphorus oxoacid can create silver mirror from

\mathrm{AgNO_3}

solution?

A

\mathrm{H_4P_2O_5}

B

\mathrm{H_4P_2O_7}

C

\mathrm{(HPO_3)_n}

D

\mathrm{H_4P_2O_6}

Correct Answer

Option A

Solution

Oxyacid having P–H bond can reduce AgNO3 to Ag.

Q127

During water-gas shift reaction

A water is evaporated in presence of catalyst.

B carbon monoxide is oxidized to carbon dioxide.

C carbon is oxidized to carbon monoxide.

D carbon dioxide is reduced to carbon monoxide.

Correct Answer

Option B

Solution

During the water-gas shift reaction, carbon monoxide (CO) + H2 reacts with steam (H2O) to produce carbon dioxide (CO2) and hydrogen gas (H2).

The chemical equation for the reaction is : Therefore, option B is correct, which states that carbon monoxide is oxidized to carbon dioxide.

This reaction is typically catalyzed by metal catalysts such as iron, nickel, or copper, which promote the reaction rate by providing a surface for the reactants to adsorb and react.

Option A is not correct as water is not evaporated during the reaction, but rather reacts with carbon monoxide to produce hydrogen gas and carbon dioxide.

Option C is not correct as carbon is not directly involved in the reaction.

Option D is also not correct as carbon dioxide is not reduced to carbon monoxide during the water-gas shift reaction.

Q128

For a good quality cement, the ratio of silica to alumina is found to be :

A 1.5

B 2

C 3

D 4.5

Correct Answer

Option C

Solution

For good quality cement, the ratio of silica $\left(\mathrm{SlO}_2\right)$ to Alumina $\left(\mathrm{Al}_2 \mathrm{O}_3\right)$ should be between 2.5 to 4.

Q129

The correct group of halide ions which can be oxidised by oxygen in acidic medium is :

A

\mathrm{Br}^{-}

only

B

\mathrm{Cl}^{-}, \mathrm{Br}^{-}

and

\mathrm{I}^{-}

only

C

\mathrm{Br}^{-}

and

\mathrm{I}^{-}

only

D

\mathrm{I}^{-}

only

Correct Answer

Option D

Solution

Only iodide ions (I⁻) can be oxidized by oxygen in acidic medium. The correct option is : Option D :

\mathrm{I}^{-}

only The reaction is :

4 \mathrm{I}^{-}(\mathrm{aq})+4 \mathrm{H}^{+}(\mathrm{aq})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{I}_2(\mathrm{~s})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l})

In this reaction, iodide ions (I⁻) are oxidized to iodine (I₂) by oxygen in the presence of an acidic medium.

Q130

The incorrect statement from the following for borazine is :

A It can react with water.

B It is a cyclic compound.

C It has electronic delocalization.

D It contains banana bonds.

Correct Answer

Option D

Solution

Borazine (B₃N₃H₆) is an inorganic compound with a structure similar to benzene, where three boron and three nitrogen atoms form a hexagonal ring, with alternating single and double bonds, and a hydrogen atom attached to each boron and nitrogen atom.

Option A : It can react with water.

Borazine is hydrolyzed by water to form boric acid, ammonia, and hydrogen.

So, this statement is correct.

Option B : It is a cyclic compound.

Borazine has a hexagonal ring structure, making it a cyclic compound.

So, this statement is correct.

Option C : It has electronic delocalization.

The electrons in the boron-nitrogen double bonds are delocalized over the entire ring, similar to benzene.

So, this statement is correct.

Option D : It contains banana bonds.

Banana bonds are typically used to describe the unconventional, multicenter bonding in certain clusters or molecules, such as diborane (B₂H₆).

Borazine does not contain banana bonds; it has a planar hexagonal structure with alternating single and double bonds between boron and nitrogen atoms.

So, this statement is incorrect.

Thus, the incorrect statement for borazine is : It contains banana bonds.