Hydrogen — Page 6 | NEET Chemistry

Q51

The total number of isotopes of hydrogen and number of radioactive isotopes among them, respectively, are :

A 3 and 2

B 2 and 1

C 2 and 0

D 3 and 1

Correct Answer

Option D

Solution

Total number of isotopes of hydrogen is 3

\Rightarrow \,\,{}_1^1H,{}_1^2H

or

{}_1^2D,\,{}_1^3H\,\,

or

{}_1^3T

and only

{}_1^3H

or

{}_1^3T

is an Radioactive element.

Q52

In which of the following reactions, hydrogen peroxide acts as an oxidizing agent ?

A HOCl + H2O2

\to

H3O+ + Cl

-

+ O2

B I2 + H2O2 + 2OH

-

\to

2I

-

+ 2H2O + O2

C 2Mn

O_4^ -

+ 3H2O2

\to

2 MnO2 + 3O2 + 2H2O + 2OH

-

D PbS + 4H2O2

\to

PbSO4 + 4H2O

Correct Answer

Option D

Solution

Since, H2O2 gains electron to convert into H2O. Hence, H2O2 acts as an oxidizing agent.

Q53

Which one of the following statements about water is FALSE?

A Water is oxidized to oxygen during photosynthesis

B Water can act both as an acid and as a base.

C There is extensive intramolecular hydrogen bonding in the condensed phase.

D Ice formed by heavy water sinks in normal water

Correct Answer

Option C

Solution

There is extensive inter-molecular hydrogen bonding in the condensed phase instead of intra-molecular

H

-bonding.

Q54

At 298.2 K the relationship between enthalpy of bond dissociation (in kJ mol

-

1) for hydrogen (EH) and its isotope, deuterium (ED), is best described by :

A

{E_H} = {1 \over 2}{E_D}

B

{E_H} = {E_D}

C

{E_H} \simeq {E_D} - 7.5

D

{E_H} = 2{E_D}

Correct Answer

Option C

Solution

Enthalpy of bond dissociation (kJ/mole) at 298.2 K For, Hydrogen = 435.88 For, Deuterium = 443.35 $\therefore$

{E_H} \simeq {E_D} - 7.5

Q55

Identify the incorrect statement regarding heavy water :

A It reacts with Al4C3 to produce CD4 and Al(OD)3 .

B It is used as a coolant in nuclear reactors.

C It reacts with CaC2 to produce C2D2 and Ca(OD)2 .

D It reacts with SO3 to form deuterated sulphuric acid (D2SO4).

Correct Answer

Option B

Solution

Heavy water is used as moderator in nuclear reactors to control the speed of neutrons.

Q56

In which of the following reactions the hydrogen peroxide acts as a reducing agent?

A

\mathrm{M{n^{2 + }} + {H_2}{O_2} \to M{n^{4 + }} + 2O{H^ - }}

B

\mathrm{HOCl + {H_2}{O_2} \to {H_3}{O^ + } + C{l^ - } + {O_2}}

C

\mathrm{PbS + 4{H_2}{O_2} \to PbS{O_4} + 4{H_2}O}

D

\mathrm{2F{e^{2 + }} + {H_2}{O_2} \to 2F{e^{3 + }} + 2O{H^ - }}

Correct Answer

Option B

Solution

$\mathrm{HOCl}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{3} \mathrm{O}^{\oplus}+\mathrm{Cl}^{\ominus}+\mathrm{O}_{2}$ In this reaction $\mathrm{H}_{2} \mathrm{O}_{2}$ is acting as a reducing agent as $\mathrm{Cl}$ is undergoing a change in oxidation state from $+1$ to $-1$ .

Q57

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : Hydrogen is an environment friendly fuel. Reason R : Atomic number of hydrogen is 1 and it is a very light element. In the light of the above statements, choose the correct answer from the options given below :

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

B A is false but R is true

C A is true but R is false

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

Correct Answer

Option A

Solution

The correct answer is (A) Both A and R are true but R is NOT the correct explanation of A.

Assertion A is true that hydrogen is an environmentally friendly fuel because when hydrogen is combusted it produces only water vapor and no harmful pollutants or greenhouse gases.

Reason R is also true that the atomic number of hydrogen is 1 and it is a very light element.

However, it is not a correct explanation for Assertion A as the environmental friendliness of hydrogen as a fuel is not solely determined by its atomic number or weight, but rather by how it is produced, stored, and transported.

The environmental impact of hydrogen as a fuel source depends on various factors, such as the method used for its production and the emissions associated with its transportation and storage.

Q58

The products obtained from a reaction of hydrogen peroxide and acidified potassium permanganate are :

A

\mathrm{Mn}^{4+}, \mathrm{H}_{2} \mathrm{O}

only

B

\mathrm{Mn}^{2+}, \mathrm{H}_{2} \mathrm{O}

only

C

\mathrm{Mn}^{4+}, \mathrm{H}_{2} \mathrm{O}, \mathrm{O}_{2}

only

D

\mathrm{Mn}^{2+}, \mathrm{H}_{2} \mathrm{O}, \mathrm{O}_{2}

only

Correct Answer

Option D

Solution

2 \mathrm{MnO}_{4}^{-}+6 \mathrm{H}^{+}+5 \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{Mn}^{2+}+8 \mathrm{H}_{2} \mathrm{O}+5 \mathrm{O}_{2}

This reaction shows reducing action of

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

in acidic medium. The products formed are

\mathrm{Mn}^{2+}, \mathrm{H}_{2} \mathrm{O}

and

\mathrm{O}_{2}

Q59

Which one of the following methods is most suitable for preparing deionized water?

A Synthetic resin method

B Clark's method

C Calgon's method

D Permutit method

Correct Answer

Option A

Solution

Pure demineralised (de-ionized) water free from all soluble mineral salts is obtained by passing water successively through a cation exchange (in the H+ form) and an anion exchange (in the OH $-$ form) resins.

Q60

Hydrogen has three isotopes : protium (1H), deuterium (2H or D) and tritium (3H or T). They have nearly same chemical properties but different physical properties. They differ in :

A number of protons.

B atomic number.

C electronic configuration.

D atomic mass.

Correct Answer

Option D

Solution

1H, 2H and 3H have same atomic number but their atomic masses are different.

Isotopes have same atomic number (i.e. same number of protons)