Hydrogen — Page 5 | JEE Chemistry

Q41

Given below are two statements : One is labelled as Assertion A and other is labelled as Reason R. Assertion A : The dihedral angles in H2O2 in gaseous phase is 90.2

^\circ

and in solid phase is 111.5

^\circ

. Reason R : The change in dihedral angle in solid and gaseous phase is due to the difference in the intermolecular forces. Choose the most appropriate answer from the options given below for A and R.

A A is correct but R is not correct.

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

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

D A is not correct but R is correct.

Correct Answer

Option D

Solution

(a) H2O2 structure in gas phase, dihedral angle is 111.5°. (b) H2O2 structure in solid phase at 110K, dihedral angle is 90.2° Hence given statement (A) is not correct.

But statement (B) is correct.

Q42

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Isotopes of hydrogen have almost same chemical properties, but difference in their rates of reaction. Reason R : Isotopes of hydrogen have different enthalpy of bond dissociation. In the light of the above statements, choose the most appropriate answer from the options given below:

A A is not correct but R is correct

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

Correct Answer

Option D

Solution

Assertion A : Isotopes of hydrogen (protium, deuterium, and tritium) have almost the same chemical properties because they have the same number of protons and electrons, which dictate chemical behavior.

However, they differ in their rates of reaction due to differences in their atomic masses, which affect reaction kinetics.

Reason R : The isotopes of hydrogen have different enthalpy of bond dissociation due to their differences in atomic mass.

The stronger bond in deuterium compared to protium, for example, leads to higher bond dissociation enthalpy.

This, in turn, influences the rate of reactions involving these isotopes, as breaking the bonds requires different amounts of energy.

Therefore, the correct answer is Both A and R are correct, and R is the correct explanation of A.

Q43

Which of the following statements in relation to the hydrogen atom is correct?

A 3s orbital is lower in energy than 3p orbital

B 3p orbital is lower in energy than 3d orbital

C 3s and 3p orbitals are of lower energy than 3d orbital

D 3s, 3p and 3d orbitals all have the same energy

Correct Answer

Option D

Solution

NOTE : In one electron species, such as

H

-atom, the energy of orbital depends only on the principal quantum number,

n.

Hence answer

(d)

i.e.

is

2s = 2p < 3s = 3p = 3d < 4s = 4p = 4d = 4f

Q44

The correct statements about H2O2 are : (A) used in the treatment of effluents. (B) used as both oxidising and reducing agents. (C) the two hydroxyl groups lie in the same plane. (D) miscible with water. Choose the correct answer from the options given below :

A (A), (C) and (D) only

B (A), (B), (C) and (D)

C (A), (B) and (D) only

D (B), (C) and (D) only

Correct Answer

Option C

Solution

H2O2 act as both oxidising and reducing agent.

H2O2 is miscible with water due to open book like structure both -OH group are not in the same plane H2O2 used in the treatment of effluents.

Q45

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.

Q46

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.

Q47

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.

Q48

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

Q49

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.

Q50

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 $-1$ .