Hydrogen — Page 2 | NEET Chemistry

Q11

The synonym for water gas when used in the production of methanol is :

A fuel gas

B laughing gas

C syn gas

D natural gas

Correct Answer

Option C

Solution

H2O(g) + C $\to$ CO + H2 The gaseous mixture CO + H2 which is produced when steam is passed over red hot coke and this mixture called water gas or synthesis gas or syn gas.

Q12

The correct statements among (a) to (d) are : (a) saline hydrides produce H2 gas when reacted with H2O. (b) reaction of LiAlH4 with BF3 leads to B2H6. (c) PH3 and CH4 are electron - rich and electron - precise hydrides, respectively. (d) HF and CH4 are called as molecular

A (a), (b), (c) and (d)

B (a), (c) and (d) only

C (c) and (d) only

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

Correct Answer

Option A

Solution

(a) NaH + H2O $\to$ NaOH + H2 (b) 3LiAlH4 + 4BF3 $\to$ 2B2H6 + 3LiF + 3AlF3 (c) PH3 is electron rich due to one lone pair while CH4 is electron precise hydride. (d) HF and CH4 are molecular hydrides.

Q13

The strength of 11.2 volume solution of H2O2 is : [Given that molar mass of H = 1 g mol–1 and O = 16 g mol–1]

A 3.4%

B 34%

C 13.6%

D 1.7%

Correct Answer

Option A

Solution

Strength means

{{Weight} \over {Volume}}

%. Molarity of H2O2 =

{{volume\,strength} \over {11.2}}

=

{{11.2} \over {11.2}}

= 1 M = 34 gm/lit In 1000 ml solution 34 gm H2O2 present $\therefore$ In 100 ml solution 3.4 gm H2O2 present.

Q14

Which of the following equation depicts the oxidizing nature of H2O2?

A

C{l_2} + {H_2}{O_2} \to 2HCl + {O_2}

B

KI{O_4} + {H_2}{O_2} \to KI{O_3} + {H_2}O + {O_2}

C

2{I^ - } + {H_2}{O_2} + 2{H^ + } \to {I_2} + 2{H_2}O

D

{I_2} + {H_2}{O_2} + 2O{H^ - } \to 2{I^ - } + 2{H_2}O + {O_2}

Correct Answer

Option C

Solution

2{I^ - } + {H_2}{O_2} + 2{H^ + } \to {I_2} + 2{H_2}O

Oxygen reduces from –1 to –2.

So, its reduction will takes place.

Hence it will behave as oxidising agent or it shows oxidising nature.

While in other option it change from (–1) to 0.

Q15

Statements about heavy water are given below : A. Heavy water is used in exchange reactions for the study of reaction mechanisms. B. Heavy water is prepared by exhaustive electrolysis of water. (C) Heavy water has higher boiling point than ordinary water. (D) Viscosity of H2O is greater than D2O. Choose the most appropriate answer from the options given below :

A A, B, and C only

B A and C only

C A and D only

D A and B only

Correct Answer

Option A

Solution

Viscosity of D2O is greater than H2O. B.P. of D2O is greater than H2O.

Q16

Which of the following could act as a propellant for rockets?

A Liquid oxygen + liquid argon

B Liquid hydrogen + liquid oxygen

C Liquid nitrogen + liquid oxygen

D Liquid hydrogen + liquid nitrogen

Correct Answer

Option B

Solution

Liquid hydrogen and liquid oxygen are used as excellent fuel for rockets.

{H_2}\left( \ell \right)

has low mass and high enthalpy of combustion whereas oxygen is a strong supporter of combustion.

Q17

In context with the industrial preparation of hydrogen from water gas (CO + H2), which of the following is the correct statement?

A CO and H2 are fractionally separated using differences in their densities

B CO is removed by absorption in aqueous Cu2Cl2 solution

C H2 is removed through occlusion with Pd

D CO is oxidised to CO2 with steam in the presence of a catalyst followed by absorption of CO2 in alkali

Correct Answer

Option D

Solution

On the industrial scale hydrogen is prepared from water gas according to following reaction sequence

\underbrace {CO + {H_2}}_{water\,\,\,gas} + \underbrace {{H_2}O}_{\left( {steam} \right)}\,\,\overset{{catalyst}}\longrightarrow C{O_2} + 2{H_2}

\,\,\,\,\,\,\,\,\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{\left( {alkali} \right)}^{2NaOH}} N{a_2}C{O_3} + {H_2}O

From the above it is clear that

CO

is first oxidised to

C{O_2}

which is then ansorbed in

NaOH.

Q18

Very pure hydrogen (99.9%) can be made by which of the following processes?

A Reaction of methane with steam

B Mixing natural hydrocarbons of high molecular weight

C Electrolysis of water

D Reaction of salt like hydrides with water

Correct Answer

Option D

Solution

Very pure hydrogen (99.9%) can be prepared by the action of water on any hydrides i.e, sodium hydride(NaH), Calcium Hydride(CaH2) etc.

NaH + {H_2}O \to NaOH + {H_2}

(very pure Hydrogen) By electrolysis of water we get 99.5% pure hydrogen. 2H2O

\overset{{Electrolysis}}\longrightarrow

2H2 + O2 Note : By electrolysis of water we can't get 99.9% pure hydrogen we only get around 99.5% pure hydrogen.

That is why option (C) is wrong.

Q19

The metal that gives hydrogen gas upon treatment with both acid as well as base is :

A mercury

B zinc

C iron

D magnesium

Correct Answer

Option B

Solution

Zn + 2HCl $\to$ ZnCl2 + H2 Zn + NaOH $\to$ Na2ZnO2 + H2 Here zinc(Zn) is amphoteric metal, that is why it reacts with both acid and base.

Q20

100 mL of a water sample contains 0.81 g of calcium bicrabonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO3 is : (Molar mass of calcium bicarbonate is 162 g mol–1 and magnesium bicarbonate is 146 g mol–1)

A 1,000 ppm

B 100 ppm

C 10,000 ppm

D 5,000 ppm

Correct Answer

Option C

Solution

Here hardness of water is expressed in terms of CaCO3.

$\therefore$ Equivalent of CaCO3 = Equivalent of Ca(HCO3)2 + Equivalent of Mg(HCO3)2 $\Rightarrow$ 2 $\times$

{W \over {100}}

=

{{0.81} \over {162}} \times 2 + {{0.73} \over {146}} \times 2

$\Rightarrow$ W = 1 gm Volume of water = 100 mL $\therefore$ Mass of water = 100 g $\therefore$ Hardness =

{{1.0} \over {100}} \times {10^6}

= 10000 ppm