JEE Advanced Chemistry Question (2024) — Solution

Step-by-step solution

Option A: \( CO _2, C _2 H _4, NO \) and HCl 1. \( CO _2\) : Carbon dioxide follows the octet rule. Carbon forms double bonds with two oxygen atoms, allowing it to have 8 electrons in its valence shell. 2. \( C _2 H _4\) : Ethylene follows the octet rule. Each carbon forms a double bond with the other carbon and single bonds with two hydrogen atoms, resulting in 8 electrons in the valence shell of the carbons. 3. NO: Nitric oxide does not follow the octet rule. It has an odd number of electrons, making it a free radical. 4. HCl: Hydrogen chloride follows the octet rule. Chlorine has 8 electrons in its valence shell when bonded with hydrogen. Thus, three molecules \( CO _2, C _2 H _4\), and HCl follow the octet rule here. Option B: \( NO _2, O _3, HCl \) and \( H _2 SO _4\) 1. \( NO _2\) : Nitrogen dioxide does not follow the octet rule. It has an odd number of electrons. 2. \( O _3\) : Ozone follows the octet rule. It has a resonance structure that allows each oxygen atom to have 8 electrons in its valence shell. 3. HCl: As mentioned, hydrogen chloride follows the octet rule. 4. \( H _2 SO _4\) : Sulfuric acid follows the octet rule. All atoms achieve stable configurations through bonding. Thus, three molecules \( O _3, HCl \), and \( H _2 SO _4\) follow the octet rule in this option. Option C: \( BCl _3, NO _2, NO _2\) and \( H _2 SO _4\) 1. \( BCl _3\) : Boron trichloride does not follow the octet rule. Boron has only 6 electrons in its valence shell. 2. NO: As mentioned, nitric oxide does not follow the octet rule. 3. \( NO _2\) : As mentioned, nitrogen dioxide does not follow the octet rule. 4. \( H _2 SO _4\) : Sulfuric acid follows the octet rule. Thus, only one molecule, \( H _2 SO _4\). follows the octet rule in this option. Option D: \( CO _2, BCl _3, O _3\) and \( C _2 H _4\) 1. \( CO _2\) : As mentioned, carbon dioxide follows the octet rule. 2. \( BCl _3\) : As mentioned, boron trichloride does not follow the octet rule. 3. \( O _3\) : As mentioned, ozone follows the octet rule. 4. \( C _2 H _4\) : As mentioned, ethylene follows the octet rule. Thus, three molecules \( CO _2, O _3\), and \( C _2 H _4\) follow the octet rule in this option. Conclusion: The correct options are Option A and Option D, both having at least three molecules that follow the octet rule.