Hydrogen Quiz - ICSE Class 9 Chemistry

Free practice quiz: Hydrogen (ICSE Class 9 Chemistry). 49 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. In the synthesis of ammonia by Haber's process, the equilibrium is favoured by:

   1. High temperature and high pressure
   2. Low temperature and low pressure
   3. High temperature and low pressure
   4. Low temperature and high pressure
   Show answer

   Answer: D. Low temperature and high pressure

   The synthesis of ammonia (N2 + 3H2 <=> 2NH3) is an exothermic reaction. According to Le Chatelier's principle, a lower temperature favours the forward (exothermic) reaction, thus increasing the yield of ammonia. The reaction also involves a decrease in the number of moles (4 moles of reactants to 2 moles of product), so an increase in pressure will shift the equilibrium to the right, favouring the formation of ammonia.

2. What is the primary reason for the unusual position of hydrogen in the periodic table?

   1. Its low atomic number
   2. Its ability to lose one electron to form H⁺, similar to alkali metals
   3. Its ability to gain one electron to form H⁻, similar to halogens
   4. Both B and C
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   Answer: D. Both B and C

   Hydrogen's unique placement in the periodic table is due to its dual nature. It can lose one electron to form a cation (H⁺), exhibiting properties similar to alkali metals (Group 1). It can also gain one electron to form an anion (H⁻), resembling halogens (Group 17) in its reactivity. This ability to participate in both types of bonding contributes to its anomalous position.

3. Hydrogen bonding, a strong intermolecular force, occurs between hydrogen and highly electronegative atoms like:

   1. Carbon and Nitrogen
   2. Oxygen, Nitrogen, and Fluorine
   3. Sulfur and Chlorine
   4. Phosphorus and Boron
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   Answer: B. Oxygen, Nitrogen, and Fluorine

   Hydrogen bonding is a special type of dipole-dipole interaction that occurs when a hydrogen atom bonded to a highly electronegative atom (like O, N, or F) is attracted to a lone pair of electrons on another electronegative atom in a different molecule or within the same molecule. This phenomenon is crucial in determining the properties of water, ammonia, and HF.

4. The 'autoionization' of hydrogen refers to:

   1. The reaction of hydrogen with itself
   2. The formation of H⁺ and H⁻ ions from a hydrogen molecule
   3. The dissociation of hydrogen into atomic hydrogen
   4. The reversible reaction of hydrogen with oxygen
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   Answer: B. The formation of H⁺ and H⁻ ions from a hydrogen molecule

   Autoionization of hydrogen, though extremely rare under normal conditions, refers to the hypothetical or theoretical process where a hydrogen molecule (H₂) spontaneously dissociates into a proton (H⁺) and a hydride ion (H⁻). This is a conceptual idea related to the extreme conditions or theoretical models.

5. The most stable allotrope of hydrogen at room temperature and pressure is:

   1. Ortho-hydrogen
   2. Para-hydrogen
   3. Atomic hydrogen
   4. Metallic hydrogen
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   Answer: B. Para-hydrogen

   At room temperature, a mixture of ortho- and para-hydrogen exists, with ortho-hydrogen being more abundant. However, at very low temperatures (below 20 K), para-hydrogen becomes the dominant and more stable form because its nuclear spins are antiparallel, resulting in a lower energy state.

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