Q.1 What is the molecular formula of hydrogen gas?
H
H2
H2O
HO2
Explanation - Hydrogen exists as a diatomic molecule (H2) under normal conditions.
Correct answer is: H2
Q.2 Which method is commonly used for the industrial production of hydrogen?
Electrolysis of water
Photosynthesis
Friedel-Crafts reaction
Haber process
Explanation - Hydrogen is produced industrially mainly by water electrolysis and steam reforming of hydrocarbons.
Correct answer is: Electrolysis of water
Q.3 Which element is hydrogen most similar to in terms of electronic configuration?
Helium
Lithium
Oxygen
Carbon
Explanation - Hydrogen has one electron like helium's outer shell, showing similarity in electronic configuration.
Correct answer is: Helium
Q.4 Hydrogen reacts with nitrogen to form which compound under suitable conditions?
Ammonia
Hydrazine
Nitric acid
Urea
Explanation - Hydrogen reacts with nitrogen under high temperature and pressure in the presence of a catalyst to form ammonia (NH3).
Correct answer is: Ammonia
Q.5 Which property of hydrogen makes it useful as a rocket fuel?
High density
High flammability
High solubility in water
Low reactivity
Explanation - Hydrogen is highly flammable and releases large amounts of energy on combustion, making it ideal for rocket fuel.
Correct answer is: High flammability
Q.6 Which catalyst is commonly used in the hydrogenation of vegetable oils?
Platinum
Palladium
Nickel
Copper
Explanation - Nickel is widely used as a catalyst in the hydrogenation of unsaturated fats to saturated fats.
Correct answer is: Nickel
Q.7 What is the bond order of H2 molecule?
1
2
3
0
Explanation - H2 has a single covalent bond between the two hydrogen atoms, giving a bond order of 1.
Correct answer is: 1
Q.8 Hydrogen forms an acidic solution when dissolved in water in the form of:
H+
OH-
H2O2
H3O+
Explanation - When hydrogen ions are dissolved in water, they combine with water molecules to form hydronium ions (H3O+), giving an acidic solution.
Correct answer is: H3O+
Q.9 Which is the most abundant isotope of hydrogen?
Protium
Deuterium
Tritium
Hydron
Explanation - Protium (¹H) is the most common isotope of hydrogen, consisting of only one proton and no neutrons.
Correct answer is: Protium
Q.10 Which form of hydrogen is radioactive?
Protium
Deuterium
Tritium
All are stable
Explanation - Tritium (³H) is a radioactive isotope of hydrogen with a half-life of about 12.3 years.
Correct answer is: Tritium
Q.11 Hydrogen gas is stored in cylinders under high pressure because:
It is highly soluble in water
It is very dense
It is very light and diffuses rapidly
It is highly reactive with air at room temperature
Explanation - Hydrogen is the lightest gas and diffuses quickly, so storing it under high pressure in cylinders ensures safe and efficient storage.
Correct answer is: It is very light and diffuses rapidly
Q.12 Which reaction produces hydrogen gas when a metal reacts with water?
2Na + 2H2O → 2NaOH + H2
Zn + HCl → ZnCl2 + H2O
Cu + H2O → CuO + H2
Fe + H2 → FeH2O
Explanation - Alkali metals react vigorously with water to produce hydrogen gas and a hydroxide.
Correct answer is: 2Na + 2H2O → 2NaOH + H2
Q.13 Which of the following is true about hydrogen bonding?
It occurs in H2 molecule
It occurs in HF, H2O, NH3 molecules
It occurs in noble gases
It is a type of ionic bond
Explanation - Hydrogen bonding occurs in molecules where hydrogen is covalently bonded to highly electronegative atoms like F, O, or N.
Correct answer is: It occurs in HF, H2O, NH3 molecules
Q.14 Which of the following is an industrial use of hydrogen?
Ammonia synthesis
Glass making
Bleaching agent
All of the above
Explanation - Hydrogen is used in ammonia synthesis, hydrogenation of oils, glass manufacturing, and as a reducing agent in metallurgy.
Correct answer is: All of the above
Q.15 What is the oxidation state of hydrogen in metal hydrides like NaH?
+1
0
-1
+2
Explanation - In metal hydrides, hydrogen has an oxidation state of -1 because it gains an electron from the metal.
Correct answer is: -1
Q.16 Which reaction represents hydrogen as a reducing agent?
CuO + H2 → Cu + H2O
2H2 + O2 → 2H2O
HCl + NaOH → NaCl + H2O
H2 + Cl2 → 2HCl
Explanation - Hydrogen acts as a reducing agent by reducing metal oxides to metals while itself getting oxidized to water.
Correct answer is: CuO + H2 → Cu + H2O
Q.17 Which property of hydrogen makes it unique among elements?
It forms only ionic bonds
It can form both positive and negative ions
It is the heaviest gas
It is a liquid at room temperature
Explanation - Hydrogen is unique because it can exist as H+ (proton) or H− (hydride ion), depending on the compound.
Correct answer is: It can form both positive and negative ions
Q.18 What is the density of hydrogen gas at STP compared to air?
Much higher
Slightly higher
Much lower
Same as air
Explanation - Hydrogen is the lightest element and its density is about 0.09 g/L at STP, much lower than air (~1.29 g/L).
Correct answer is: Much lower
Q.19 Which of the following metals does NOT react with cold water to produce hydrogen?
Sodium
Potassium
Calcium
Copper
Explanation - Copper is a less reactive metal and does not react with cold water to produce hydrogen.
Correct answer is: Copper
Q.20 Hydrogen forms hydrides with other elements. Which type of hydride does lithium form?
Ionic hydride
Covalent hydride
Metallic hydride
Complex hydride
Explanation - Lithium reacts with hydrogen to form ionic hydrides, where hydrogen is present as H−.
Correct answer is: Ionic hydride
Q.21 Which of the following reactions is used for laboratory preparation of hydrogen?
Zn + HCl → ZnCl2 + H2
Na + H2O → NaOH + H2
Electrolysis of NaCl solution
Mg + O2 → MgO
Explanation - Zinc reacts with dilute hydrochloric acid to release hydrogen gas, commonly used in labs.
Correct answer is: Zn + HCl → ZnCl2 + H2
Q.22 Which statement about hydrogen flame is correct?
It is luminous and very hot
It is colorless and very hot
It is blue and cool
It is yellow and smoky
Explanation - Hydrogen burns with a pale blue or nearly invisible flame, producing a very high temperature.
Correct answer is: It is colorless and very hot
Q.23 Which of the following is a hydrogen storage method for fuel cells?
Compressed gas
Metal hydrides
Liquid hydrogen
All of the above
Explanation - Hydrogen can be stored as compressed gas, liquid hydrogen, or in metal hydrides for use in fuel cells.
Correct answer is: All of the above
Q.24 Which element is present in the fuel of a hydrogen-oxygen fuel cell along with oxygen?
Hydrogen
Nitrogen
Carbon
Helium
Explanation - In a hydrogen-oxygen fuel cell, hydrogen reacts with oxygen to produce electricity, water, and heat.
Correct answer is: Hydrogen
Q.25 Which statement about hydrogen's position in the periodic table is correct?
It is a noble gas
It is placed in Group 1
It is a halogen
It is a transition metal
Explanation - Hydrogen is placed in Group 1 because it has one valence electron, but it is not an alkali metal.
Correct answer is: It is placed in Group 1