p-Block Elements — Page 11 | JEE Chemistry

Q101

Borazine, also known as inorganic benzene, can be prepared by the reaction of 3-equivalents of "

X

" with 6-equivalents of "

Y

". "

X

" and "

Y

", respectively are :

A

\mathrm{B}(\mathrm{OH})_{3}

and

\mathrm{NH}_{3}

B

\mathrm{B}_{2} \mathrm{H}_{6}

and

\mathrm{NH}_{3}

C

\mathrm{B}_{2} \mathrm{H}_{6}

and

\mathrm{HN}_{3}

D

\mathrm{NH}_{3}

and

\mathrm{B}_{2} \mathrm{O}_{3}

Correct Answer

Option B

Solution

3 \mathrm{~B}_{2} \mathrm{H}_{6}+6 \mathrm{NH}_{3} \rightarrow \underset{\text{ (Borazine) }}{2 \mathrm{~B}_{3} \mathrm{N}_{3} \mathrm{H}_{6}}

Q102

When borax is heated with

\mathrm{CoO}

on a platinum loop, blue coloured bead formed is largely due to :

A

\mathrm{B}_{2} \mathrm{O}_{3}

B

\mathrm{Co}\left(\mathrm{BO}_{2}\right)_{2}

C

\mathrm{CoB}_{4} \mathrm{O}_{7}

D

\mathrm{Co}\left[\mathrm{B}_{4} \mathrm{O}_{5}(\mathrm{OH})_{4}\right]

Correct Answer

Option B

Solution

$\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{NaBO}_{2}+\mathrm{B}_{2} \mathrm{O}_{3}$ $\mathrm{B}_{2} \mathrm{O}_{3}+\mathrm{CoO} \rightarrow \mathrm{Co}\left(\mathrm{BO}_{2}\right)_{2}$

Q103

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion : Boric acid is a weak acid. Reason R : Boric acid is not able to release

\mathrm{H}^{+}

ion on its own. It receives

\mathrm{OH}^{-}

ion from water and releases

\mathrm{H}^{+}

ion. In the light of the above statements, choose the most appropriate answer from the options given below.

A Both A and R are true and R is the correct explanation of A.

B Both A and R are true but R is NOT the correct explanation of A.

C A is correct but R is not correct.

D A is not correct but R is correct.

Correct Answer

Option A

Solution

Boric acid is a weak acid

\mathrm{H}_{3} \mathrm{BO}_{3}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons\left[\mathrm{B}(\mathrm{OH})_{4}\right]^{\ominus}+\mathrm{H}^{\oplus}

Boric acid is not able to release

\mathrm{H}^{+}

ion on its own. It receives

\mathrm{OH}^{-}

ion from water and releases

\mathrm{H}^{+}

ion as shown in the above reaction. Hence, Both A and R are correct and R is the correct explanation of A.

Q104

Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Activated charcoal adsorbs SO2 more efficiently than CH4. Reason R : Gases with lower critical temperatures are readily adsorbed by activated charcoal. In the light of the above statements, choose the correct answer from the options given below.

A Both A and R are correct and R is the correct explanation of A.

B Both A and R are correct but R is NOT the correct explanation of A.

C A is correct but R is not correct.

D A is not correct but R is correct.

Correct Answer

Option C

Solution

More polar gases easily adsorbs on activated charcoal.

And more polar gases has more (higher) critical temperature as compared to non-polar or less polar gases.

$\therefore$ Gases with higher critical temperature adsorbed more.

Q105

Given below are two statements. Statement I: The chlorides of

\mathrm{Be}

and

\mathrm{Al}

have Cl-bridged structure. Both are soluble in organic solvents and act as Lewis bases. Statement II: Hydroxides of

\mathrm{Be}

and

\mathrm{Al}

dissolve in excess alkali to give beryllate and aluminate ions. In the light of the above statements, choose the correct answer from the options given below.

A Both Statement I and Statement II are true.

B Both Statement I and Statement II are false.

C Statement I is true but Statement II is false.

D Statement I is false but Statement II is true.

Correct Answer

Option D

Solution

Chlorides of $\mathrm{Be}$ and $\mathrm{Al}$ are $\mathrm{BeCl}_{2}$ and $\mathrm{AlCl}_{3}$ and they have electron deficiency at central atom and behave as the Lewis acids.

\begin{aligned} & \mathrm{BeCl}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow\left[\underset{\text{ beryllate ion }}{\mathrm{Be}(\mathrm{OH})_{4}}\right]^{2-} \\\\ & \mathrm{AlCl}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow\left[\underset{\text{ aluminate ion }}{\mathrm{Al}(\mathrm{OH})_{4}}\right]^{-} \end{aligned}

Q106

Which oxoacid of phosphorous has the highest number of oxygen atoms present in its chemical formula?

A Pyrophosphorus acid

B Hypophosphoric acid

C Phosphoric acid

D Pyrophosphoric acid

Correct Answer

Option D

Solution

Pyrophosphorus acid $\rightarrow \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{5}$ Hypophosphoric acid $\rightarrow \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}$ Phosphoric acid $\rightarrow \mathrm{H}_{3} \mathrm{PO}_{4}$ Pyrophosphoric acid $\rightarrow \mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{7}$

Q107

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Boron is unable to form

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

. Reason (R) : Size of B is very small. In the light of the above statements, choose the correct answer from the options given below :

A Both (A) and (R) are true and (R) is the correct explanation of (A)

B Both (A) and (R) are 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

Correct Answer

Option B

Solution

The outer most shell of Boron is 2 and its maximum covalency is $4 .$ Therefore, boron cannot form $\mathrm{BF}_{6}^{3-}$ .

Hence Assertion is correct Boron is the first element of group-13 of modern periodic table.

It is very small in size.

But it does not provide correct explanation of Assertion

Q108

Concentrated

\mathrm{HNO}_{3}

reacts with Iodine to give :

A HI,

\mathrm{NO}_{2}

and

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

B

\mathrm{HIO}_{2}, \mathrm{~N}_{2} \mathrm{O}

and

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

C

\mathrm{HIO}_{3}, \mathrm{NO}_{2}

and

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

D

\mathrm{HIO}_{4}, \mathrm{NO}_{2}

and

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

Correct Answer

Option C

Solution

$\mathrm{I}_2+10 \mathrm{HNO}_{3(\mathrm{conc})} \to 2 \mathrm{HIO}_3+10 \mathrm{NO}_2+4 \mathrm{H}_2 \mathrm{O}$

Q109

Dinitrogen and dioxygen, the main constituents of air do not react with each other in atmosphere to form oxides of nitrogen because :

A

\mathrm{N}_{2}

is unreactive in the condition of atmosphere.

B Oxides of nitrogen are unstable.

C Reaction between them can occur in the presence of a catalyst.

D The reaction is endothermic and require very high temperature.

Correct Answer

Option D

Solution

$\mathrm{N}_{2}$ is unreactive, its reaction with oxides is endothermic and require very high temperature.

\mathrm{N}_2+\mathrm{O}_2 \overset{{(1483-2000 \mathrm{~K})}}\leftrightharpoons 2 \mathrm{NO}

(Endothermic and feasible at high temperature)

Q110

In liquation process used for tin (Sn), the metal :

A is reacted with acid.

B is dissolved in water.

C is brought to molten form which is made to flow on a slope.

D is fused with NaOH

Correct Answer

Option C

Solution

Liquation In this method a low melting metal like tin can be made to flow on a sloping surface.

In this way it is separated from higher melting impurities