Hydrogen — Page 7 | JEE Chemistry

Q61

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

acts as a reducing agent in :

A

\mathrm{Mn}^{2+}+2 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{MnO}_{2}+2 \mathrm{H}_{2} \mathrm{O}

B

2 \mathrm{Fe}^{2+}+2 \mathrm{H}^{+}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{Fe}^{3+}+2 \mathrm{H}_{2} \mathrm{O}

C

\mathrm{Na}_{2} \mathrm{S}+4 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+4 \mathrm{H}_{2} \mathrm{O}

D

2 \mathrm{NaOCl}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}

Correct Answer

Option D

Solution

$\mathrm{H}_{2} \mathrm{O}_{2}$ act as a reducing agent. $2 \stackrel{+1}{\mathrm{Na}}\stackrel{-2}{\mathrm{O}} \stackrel{+1}{\mathrm{Cl}}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}$ $\mathrm{Cl}$ from (+1) state changes to $\mathrm{Cl}^{-1}$ .

Q62

Boiling of hard water is helpful in removing the temporary hardness by converting calcium hydrogen carbonate and magnesium hydrogen carbonate to :

A CaCO3 and Mg(OH)2

B CaCO3 and MgCO3

C Ca(OH)2 and MgCO3

D Ca(OH)2 and Mg(OH)2

Correct Answer

Option A

Solution

\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2} \stackrel{\Delta}{\longrightarrow} \mathrm{CaCO}_{3} \downarrow+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \uparrow

\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2} \stackrel{\mathrm{A}}{\longrightarrow} \mathrm{Mg}(\mathrm{OH})_{2}+2 \mathrm{CO}_{2} \uparrow

Q63

Given below are two statements : Statement I :

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

is used in the synthesis of Cephalosporin Statement II :

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

is used for the restoration of aerobic conditions to sewage wastes. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement

\mathbf{I}

is incorrect but Statement

\mathbf{II}

is correct

B Statement

\mathbf{I}

is correct but Statement

\mathbf{II}

is incorrect

C Both Statement

\mathbf{I}

and Statement

\mathbf{II}

are incorrect

D Both Statement

\mathbf{I}

and Statement

\mathbf{II}

are correct

Correct Answer

Option D

Solution

H2O2 is used in the synthesis of hydroquinone, tartaric acid and certain food products and pharmaceuticals (cephalosporin).

Nowadays it is also used in environmental (green) chemistry for example in pollution control treatment of domestic and industrial effluents, oxidation of cyanides restoration of aerobic condition to sewage waste.

Hence both statements are correct.

Q64

Given below are two statements: one is labelled as Assertion

\mathbf{A}

and the other is labelled as Reason

\mathbf{R}

Assertion A : Physical properties of isotopes of hydrogen are different. Reason R : Mass difference between isotopes of hydrogen is very large. In the light of the above statements, choose the correct answer from the options given below:

A

\mathbf{A}

is true but

\mathbf{R}

is false

B Both

\mathbf{A}

and

\mathbf{R}

are true but

\mathbf{R}

is NOT the correct explanation of

\mathbf{A}

C

\mathbf{A}

is false but

\mathbf{R}

is true

D Both

\mathbf{A}

and

\mathbf{R}

are true and

\mathrm{R}

is the correct explanation of

\mathbf{A}

Correct Answer

Option D

Solution

Assertion A: The physical properties of isotopes of hydrogen are different.

This is true because the different isotopes of hydrogen have different masses.

The mass of an atom determines its physical properties, such as its melting point, boiling point, and density.

Reason R: The mass difference between isotopes of hydrogen is very large.

This is also true.

The three isotopes of hydrogen are protium (1H), deuterium (2H), and tritium (3H).

Protium has a mass of 1, deuterium has a mass of 2, and tritium has a mass of 3.

The difference in mass between these isotopes is relatively large, which is why they have different physical properties.

The reason is the correct explanation of the assertion because it explains why the physical properties of the isotopes of hydrogen are different.

The different masses of the isotopes cause them to have different physical properties.

Q65

Hydrogen peroxide oxidises [Fe(CN)6]4- to [Fe(CN)6]3- in acidic medium but reduces [Fe(CN)6]3- to [Fe(CN)6]4- in alkaline medium. The other products formed are, respectively :

A H2O and (H2O + OH-)

B (H2O + O2) and H2O

C (H2O + O2) and (H2O + OH-)

D H2O and (H2O + O2)

Correct Answer

Option D

Solution

In acidic medium, [Fe(CN)6]-3 is oxidise to [Fe(CN)6]-3 by H2O2.

So H2O2 will perform reduction reaction.

Reduction reaction of H2O2.

{H_2}O_2^{ - 1}\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{{\mathop{\rm Re}\nolimits} duction}} {H_2}\mathop O\limits^{ - 2}

Complete reaction : [ Fe (CN)6 ] $-$ 4 + H2O2 + 2H+

\overset{\,}\longrightarrow

2 [ Fe(CN)6 ] $-$ 3 + 2H2O In alkaline medium, [Fe (CN)6] $-$ 3 reduce to [ Fe(CN)6 ] $-$ 4 So H2O2 will oxidize.

Oxidization of H2O2 : H2

O_2^{ - 1}

\overset{\,}\longrightarrow

O_2^0

Complete reaction : [Fe (CN)6 ] $-$ 3 + H2O2 + 2OH $-$

\overset{\,}\longrightarrow

2 [Fe(CN)6 ] $-$ 4 + 2H2O + O2 So, ion acidic medium H2O and in alkaline medium O2 + H2O are produced as by product.

Q66

From the following statements regarding H2O2, choose the incorrect statement :

A It decomposes on exposure to light

B It has to be stored in plastic or wax lined glass bottles in dark

C It has to be kept away from dust

D It can act only as an oxidizing agent

Correct Answer

Option D

Solution

{H_2}{O_2}

has oxidizing and reducing properties both.

Q67

Given below are two statements: Statement-I : Methane and steam passed over a heated

\mathrm{Ni}

catalyst produces hydrogen gas. Statement-II : Sodium nitrite reacts with

\mathrm{NH}_{4} \mathrm{Cl}

to give

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

and

\mathrm{NaCl}

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

A Statement I is correct but Statement II is incorrect

B Both the statements I and II are incorrect

C Both the statements I and II are correct

D Statement I is incorrect but Statement II is correct

Correct Answer

Option C

Solution

Let's consider each statement: Statement-I : Methane (CH₄) and steam (H₂O) can indeed react in the presence of a heated nickel catalyst to produce carbon monoxide (CO) and hydrogen gas (H₂).

This is known as the steam reforming or steam methane reforming reaction and is industrially significant for hydrogen production.

Hence, Statement-I is correct.

Statement-II : Sodium nitrite (NaNO₂) reacts with ammonium chloride (NH₄Cl) to produce nitrogen gas (N₂), water (H₂O), and sodium chloride (NaCl).

This is a standard reaction that is often used in inorganic chemistry to produce nitrogen gas.

Hence, Statement-II is also correct.

Therefore, the correct answer is Option C: Both the statements I and II are correct.

Q68

Identify the reaction which does not liberate hydrogen :

A Reaction of zinc with aqueous alkali.

B Electrolysis of acidified water using Pt electrodes.

C Allowing a solution of sodium in liquid ammonia to stand.

D Reaction of lithium hydride with B2H6.

Correct Answer

Option D

Solution

2LiH + B2H6

\overset{{Ether}}\longrightarrow

2LiBH4

Q69

The reaction of

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

with potassium permanganate in acidic medium leads to the formation of mainly :

A Mn2+

B Mn4+

C Mn3+

D Mn6+

Correct Answer

Option A

Solution

The reaction of

\mathrm{KMnO}_{4}

with

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

in acidic medium is as

\begin{aligned} 2 \mathrm{KMnO}_{4}+3 \mathrm{H}_{2} \mathrm{SO}_{4}+5 \mathrm{H}_{2} \mathrm{O}_{2} \\ & \rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+2 \mathrm{MnSO}_{4}+8 \mathrm{H}_{2} \mathrm{O}+5 \mathrm{O}_{2} \end{aligned}

\therefore \mathrm{Mn}^{2+}

will be formed as the product.

Q70

In basic medium, H2O2 exhibits which of the following reactions? (A) Mn2+

\to

Mn4+ (B) I2

\to

I

-

(C) PbS

\to

PbSO4 Choose the most appropriate answer from the options given below :

A (B) only

B (A), (B) only

C (A) only

D (A), (C) only

Correct Answer

Option B

Solution

In basic medium, oxidising action of H2O2.

Mn2+ + H2O2 $\to$ Mn+4 + 2OH– In basic medium, reducing action of H2O2.

I2 + H2O2 + 2OH– $\to$ 2I– + 2H2O + O2 In acidic medium, oxidising action of H2O2.

PbS(s) + 4H2O2(aq) $\to$ PbSO4(s) + 4H2O(l)