Hydrogen JEE Main Questions 2025: Important Practice Questions with PYQs

1.

Which one of the following statements about water is false?

(1) Water is oxidized to oxygen during photosynthesis.

(2) Water can act both as an acid and as a base.

(3) There is extensive intramolecular hydrogen bonding in the condensed phase.

(4) Ice formed by heavy water sinks in normal water.

There is extensive intermolecular hydrogen bonding in water molecules in the condensed phase. It is not intramolecular hydrogen bonding.

Hence option (3) is the correct answer.

2.

NaH is an example of

(1) metallic hydride

(2) saline hydride

(3) electron-rich hydride

(4) molecular hydride.

NaH is an example of saline hydride. Hydrides are binary compounds of the elements with hydrogen.

Hence option (2) is the answer.

3.

The chemical nature of hydrogen peroxide is

(1) oxidising and reducing agent in both acidic and basic medium

(2) oxidising agent in acidic medium, but not in basic medium

(3) oxidising and reducing agent in acidic medium, but not in basic medium

(4) reducing agent in basic medium, but not in acidic medium.

Hydrogen peroxide acts as both oxidising and reducing agent in both acidic and basic medium.

Hence option (1) is the answer.

4.

The isotopes of hydrogen are

(1) protium, deuterium and tritium

(2) protium and deuterium only

(3) deuterium and tritium only

(4) tritium and protium only.

The isotopes of hydrogen are protium, deuterium and tritium.

Hence option (1) is the answer.

5.

Hydrogen peroxide acts both as an oxidising and as a reducing agent depending upon the nature of the reacting species. In which of the following cases does H2O2 act as a reducing agent in acid medium?

(1) MnO4–

(2) SO32-

(3) KI

(4) Cr2O72-

Reducing agent is an element or compound that loses or donates an electron to an electron recipient, oxidizing agent in a redox chemical reaction.

H2O2 + MnO4– → Mn+2 +O2

Hence option (1) is the answer.

6.

Identify the incorrect statement regarding heavy water.

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

(2) It is used as a coolant in nuclear reactors.

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

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

Heavy water is used as a moderator in nuclear reactors to control the speed of neutrons. It is not used as a coolant.

Hence option (2) is the correct answer.

7.

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

(1) fuel gas

(2) natural gas

(3) laughing gas

(4) syn gas.

Water-gas is CO+H2.

It is used for the synthesis of methanol. So it is called syn gas.

Hence option (4) is the answer.

8.

Which physical property of dihydrogen is wrong?

(1) Colourless gas

(2) Odourless gas

(3) Tasteless gas

(4) Non-inflammable gas

Dihydrogen is an inflammable gas.

Hence option (4) is the correct answer.

9.

Which one of the following processes will produce hard water?

(1) Saturation of water with CaCO3

(2) Saturation of water with MgCO3

(3) Saturation of water with CaSO4

(4) Addition of Na2SO4 to water

Hard water contains calcium and Magnesium salt in the form of hydrogen carbonate, chloride and sulphate. Permanent hardness is introduced when water passes over rocks containing the sulphates or chlorides of both calcium and magnesium.

Hence option (3) is the correct answer.

10.

In the preparation of sodium peroxoborate, H2O2 is treated with sodium metaborate.

(1) 1,2,4

(2) 2,3,4

(3) 1,2,3,4

(4) 1,2,3

All the given statements are correct.

Hence option (3) is the answer.

11.

Which of the following processes can make very pure hydrogen (99.9%)?

(1) Reaction of salt like hydrides with water

(2) Reaction of methane with steam

(3) Mixing natural hydrocarbons of high molecular weight

(4) Electrolysis of water

Very pure hydrogen (99.9%) can be made by electrolysis of water using platinum electrodes in presence of small amount of acid or alkali.

2H2O(l) → 2H2(g) + O2

Hence option (4) is the answer.

12.

Determine the total number of neutrons in three isotopes of hydrogen

(1) 1

(2) 2

(3) 3

(4) 4

Number of neutrons = 0+1+2 = 3

Hence option (3) is the answer.

13.

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 ~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.

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

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

(3) (A) and (C) only

(4) (B) and (D) only

On combustion, the value of energy released per gram of liquid dihydrogen is 142kJ.

The energy released per gram of LPG is 50kJ. Statement D is wrong.

Hence option (1) is the answer.

14.

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 :

(1) (H2O + O2 ) and (H2O + OH–)

(2) H2O and (H2O + O2)

(3) H2O and (H2O + OH– )

(4) (H2O + O2 ) and H2O

[Fe(CN)6]4- reacts with hydrogen peroxide in acidic medium to form [Fe(CN)6]3- and water.

[Fe(CN)6]4- + H2O2 + 2H+ → [Fe(CN)6]3-+ 2H2O

[Fe(CN)6]3- reacts with hydrogen peroxide in alkaline medium to form [Fe(CN)6]4-, oxygen and water.

[Fe(CN)6]3- + H2O2 + 2OH– → [Fe(CN)6]4-+O2+ 2H2O

Hence option (2) is the answer.

15.

The metal that gives hydrogen gas upon treatment with both acid, as well as base, is
(1) magnesium

(2) zinc

(3) mercury

(4) iron.

Zinc is the metal that gives hydrogen gas upon treatment with both bases as well as an acid.

Hence option (2) is the correct answer.

16.

Which of the following statements are correct?

(1) On decomposition of H2O2, O2 gas is released.

(2) 2-ethylanthraquinol is used in the preparation of H2O2

(3) On heating KClO3, Pb(NO3)2, NaNO3, O2 gas is released.

(4) In the preparation of sodium peroxoborate, H2O2 is treated with sodium metaborate.

(1) 1,2,4

(2) 2,3,4

(3) 1,2,3,4

(4) 1,2,3

All the given statements are correct.

Hence option (3) is the answer.

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