Hydrogen — Page 7 | NEET Chemistry

Q61

High purity (> 99.95%) dihydrogen is obtained by :

A reaction of zinc with aqueous alkali.

B electrolysis of acidified water using platinum electrodes.

C electrolysis of warm aqueous barium hydroxide solution between nickel electrodes.

D reaction of zinc with dilute acid.

Correct Answer

Option C

Solution

High purity (>99.95 %)

\mathrm{H}_{2}

is obtained by electrolysing warm aqueous

\mathrm{Ba}(\mathrm{OH})_{2}

solution between nickel electrodes.

Q62

(A) HOCI + H2O2 → H3O+ + Cl- + O2 (B) I2 + H2O2 + 2OH- → 2I- + 2H2O + O2 Choose the correct option.

A H2O2 acts as reducing and oxidising agent respectively in equations (A) and (B).

B H2O2 act as oxidizing and reducing agent respectively in equations (A) and (B).

C H2O2 acts as oxidising agent in equations (A) and (B).

D H2O2 acts as reducing agent in equations (A) and (B).

Correct Answer

Option D

Solution

In equation (A), HOCl undergoes reduction in presence of H2O2.

Here, oxidation state of Cl changes from +1 to –1 (i.e. reduces) $\therefore$ H2O2 act as reducing agent I2 reduces to I- in presence of H2O2.

In equation (B), Here oxidation state of iodine decreases (from 0 to –1) $\therefore$ H2O2 act as reducing agent in both the equations.

Q63

The products obtained during treatment of hard water using Clark's method are :

A

\mathrm{CaCO}_{3}

and

\mathrm{MgCO}_{3}

B

\mathrm{Ca}(\mathrm{OH})_{2}

and

\mathrm{Mg}(\mathrm{OH})_{2}

C

\mathrm{CaCO}_{3}

and

\mathrm{Mg}(\mathrm{OH})_{2}

D

\mathrm{Ca}(\mathrm{OH})_{2}

and

\mathrm{MgCO}_{3}

Correct Answer

Option C

Solution

In Clark's method lime water is used

\begin{aligned} &\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+2 \mathrm{Ca}(\mathrm{OH})_2 \rightarrow 2 \mathrm{CaCO}_3+2 \mathrm{H}_2 \mathrm{O} \\\\ &\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2+2 \mathrm{Ca}(\mathrm{OH})_2 \rightarrow 2 \mathrm{CaCO}_3+\mathrm{Mg}(\mathrm{OH})_2+2 \mathrm{H}_2 \mathrm{O} \end{aligned}

Q64

Dihydrogen reacts with CuO to give :

A CuH2

B Cu

C Cu2O

D Cu(OH)2

Correct Answer

Option B

Solution

CuO + H2 $\to$ Cu + H2O (under hot conditions)

Q65

The correct statements among (a) to (d) regarding H2 as a fuel are : (a) It produces less pollutants than petrol. (b) A cylinder of compressed dihydrogen weighs

\sim

30 times more than a petrol tank producing the same amount of energy. (c) Dihydrogen is stored in tanks of metal alloys like NaNi5. (d) On combustion, values of energy released per gram of liquid dihydrogen and LPG are 50 and 142 KJ, respectively.

A (a) and (c) only

B (b) and (d) only

C (a), (b) and (c) only

D (b), (c) and (d) only

Correct Answer

Option C

Solution

(I) H2 is a 100% pollution free fuel. So, option (I) is correct. (II) Molecular weight of H2(2u).

= {1 \over {29}} \times

molecular weight of butane, C4H10 (LPG) [58u].

So, compressed H2 weighs $\sim$ 30 times more than a petrol tank and option (b) is correct.

(III) NaNi5, Ti - TiH2 etc. are used for storage of H2 in small quantities.

Thus, option (c) is correct.

(IV) On combustion values of energy released per gram of liquid dihydrogen (H2) : 142 kJ g $-$ 1, and for LPG : 50 kJ g $-$ 1.

So, option (d) is incorrect.

Q66

The functional groups that are responsible for the ion-exchange property of cation and anion exchange resins, respectively, are :

A

-

SO3H and

-

NH2

B

-

NH2 and COOH

C

-

NH2 and

-

SO3H

D

-

SO3H and

-

COOH

Correct Answer

Option A

Solution

Cation exchange resins contain large organic a molecule with –SO3H group.

In the cation exchange process H+ exchanges for Na+, Ca2+, Mg2+ and other cations present in water.

While anion exchange resins contain –NH2 in form of –NH3+ OH– where OH– exchanges for anions like Cl–, HCO3–, SO4 2–, etc.

Q67

\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 $\mathrm{Cl}^{-1}$ .

Q68

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

Q69

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.

Q70

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.