p-Block Elements — Page 4 | JEE Chemistry

Q31

Reaction of ammonia with excess Cl2 gives :

A NH4Cl and N2

B NH4Cl and HCl

C NCl3 and HCl

D NCl3 and NH4Cl

Correct Answer

Option C

Solution

NH3 + 3Cl2(excess) $\to$ NCl3 + 3HCl

Q32

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

A PCI3 and HCI are formed and the mixture warms up

B PCI5 and HCI are formed and the mixture cools down

C PH3.Cl2 is formed with warming up

D The mixture only cools down

Correct Answer

Option A

Solution

When phosphine gas (PH₃) is mixed with chlorine gas (Cl₂), the reaction between them depends on the conditions and the proportions of the reactants.

Let's consider the options : Option A : PCl₃ and HCl are formed and the mixture warms up.

When phosphine gas reacts with chlorine gas, one of the possible products is phosphorus trichloride (PCl₃) along with hydrogen chloride (HCl).

This reaction is exothermic, meaning it releases heat and causes the mixture to warm up.

Option B : PCl₅ and HCl are formed and the mixture cools down.

Phosphorus pentachloride (PCl₅) can be formed if an excess of chlorine is used, but this reaction is also exothermic.

The formation of PCl₅ is less likely with PH₃ as it requires a higher proportion of chlorine and controlled conditions.

Option C : PH₃·Cl₂ is formed with warming up.

There is no known stable compound like PH₃·Cl₂ formed directly from the reaction of phosphine and chlorine gas.

This option does not represent a typical chemical reaction product.

Option D : The mixture only cools down.

Chemical reactions between phosphine and chlorine are exothermic, so this statement is incorrect.

Based on this analysis, the most likely and correct reaction is described in Option A : PCl₃ and HCl are formed, and the mixture warms up.

This reaction is feasible and aligns with the known chemistry of phosphine and chlorine gases.

Q33

The soldiers of Napolean army while at Alps during freezing winter suffered a serious problem as regards to the tin buttons of their uniforms. White metallic tin buttons got converted to grey power. The transformation is related to :

A a change in the partial pressure of oxygen in the air

B a change in the crystalline structure of tin

C an interaction with nitrogen of the air at very low temperature

D an interaction with water vapor contained in the humid air

Correct Answer

Option B

Solution

Grey tin

\,\,\,

$\rightleftharpoons$

\,\,\,

white tin Grey tin is brittle and crumbles down to powder in very cold climate The conversion of grey tin to white tin is accompanied by increase in volume.

This is known as tin plaque or tin disease.

Q34

In silicon dioxide :

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

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

C Silicon atoms is bonded to two oxygen atoms

D there are double bonds between silicon and oxygen atoms

Correct Answer

Option A

Solution

In

Si{O_2}\,\,

(quartz), each of

O

-atom is shared between two

SiO_4^{4 + }

tetrahedra.

Q35

The structure of diborane (B2H6) contains :

A four 2c-2e bonds and two 3c-2e bonds

B two 2c-2e bonds and four 3c-2e bonds

C two 2c-2e bonds and two 3c-3e bonds

D four 2c-2e bonds and four 3c-2e bonds

Correct Answer

Option A

Solution

In diborane structure

{B_2}{H_6}

there are four

2c-2e

bonds and two

3c-2e

bonds (see structure of diborane).

Note : 2c - 2e bond means two center two electron bond and 3c - 2e bond means three center two electron bond.

Q36

Heating an aqueous solution of aluminium chloride to dryness will give :

A AlCl3

B Al2Cl6

C Al2O3

D Al(OH)Cl2

Correct Answer

Option C

Solution

The solution of aluminium chloride in water is acidic due to hydrolysis.

AlC{l_3} + 3{H_2}O\overset{\,}\longrightarrow Al{\left( {OH} \right)_3} + 3HCl.

On heating it till dryness

Al{\left( {OH} \right)_3}

is converted into

A{l_2}{O_3}

Al{\left( {OH} \right)_3}\overset{\Delta}\longrightarrow A{l_2}{O_3} + 3{H_2}O

Q37

The correct order of the thermal stability of hydrogen halides (H – X) is :

A HI > HBr > HCl > HF

B HF > HCl > HBr > HI

C HCl < HF > HBr < HI

D HI > HCl < HF < HBr

Correct Answer

Option B

Solution

The

H-X

bond strength decreases from

HF

to

HI.

i.e.

HF > HCl > HBr > HI.

Thus

HF

is most stable while

HI

is least stable. This is evident from their decompositions reaction:

HF

and

HCl

are stable upto

1473K,HBr

decreases slightly and

HI

dissociates considerably

713K.

The decreasing stability of the hydrogen halide is also reflected in the values of dissociation energy of the

H-X

bond

\begin{array}{lll}{H - F} & {H - Cl} & {H - Br} & {H - I} \\ {135kcal\,mo{l^{ - 1}}} & {103kcal\,mo{l^{ - 1}}} & {87kcal\,mo{l^{ - 1}}} & {71kcal\,mo{l^{ - 1}}} \end{array}

Q38

Which of the following statements is true?

A H3PO3 is a stronger acid than H2SO3

B In aqueous medium HF is a stronger acid than HCl

C HClO4 is a weaker acid than HClO3

D HNO3 is a stronger acid than HNO2

Correct Answer

Option D

Solution

The

\mathop {HN{O_3}}\limits^{ + 5}

is stronger than

\mathop {HN{O_2}}\limits^{ + 3} .

The more the oxidation state of

N,

the more is the acid character.

Q39

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

A HClO3 and Cl2O

B HClO2 and HClO4

C HCl and Cl2O

D HCl and HClO3

Correct Answer

Option D

Solution

During disproportionation same compound undergo simultaneous oxidation and reduction.

Q40

Regular use of which of the following fertilizer increases the acidity of soil?

A Potassium nitrate

B Urea

C Superphosphate of lime

D Ammonium sulphate

Correct Answer

Option D

Solution

\,{\left( {N{H_4}} \right)_2}S{O_4} + 2{H_2}O\overset{\,}\longrightarrow 2{H_2}S{O_4} + N{H_4}OH

{H_2}S{O_4}\,\,

is strong acid and increases the acidity of soil.