💯 Hydrogen Chapter Revision Q&A for JEE Advanced Q: What is the electron configuration of hydrogen ? A: 1s 1 . Q: What is the bond length of the H 2 molecule? A: Approximately 0.74 Å. Q: What type of bond is present in H 2 molecule? A: A sigma covalent bond formed by overlap of 1s orbitals. Q: What is the bond dissociation energy of H 2 ? A: Approximately 436 kJ/mol. Q: What is isotopes of hydrogen ? A: Protium , deuterium , and tritium . Q: What is the main use of deuterium? A: Heavy water (D 2 O) used as moderator in nuclear reactors . Q: How is hydrogen prepared in laboratory? A: Reaction of Zn with dilute H 2 SO 4 . Q: Industrial method of hydrogen production? A: Water gas reaction and steam methane reforming . Q: What is the reaction of hydrogen with oxygen? A: 2H 2 + O 2 → 2H 2 O (highly exothermic). Q: What is hydrogen’s oxidation state in H 2 O? A: +1. Q: Which is more stable, ortho-hydrogen or para-hydrogen? A: Para-hydrogen is mor...

   💯 Elimination vs Substitution Revision Q&A (Class 12 Chemistry) Q: What is a substitution reaction ? A: A reaction where an atom/group in a molecule is replaced by another atom/group. Q: What is an elimination reaction ? A: A reaction where atoms/groups are removed from a molecule to form a multiple bond. Q: Which reagents favor substitution over elimination? A: Weak bases and strong nucleophiles favor substitution. Q: Which reagents favor elimination over substitution? A: Strong bulky bases favor elimination. Q: What is the leaving group in substitution/elimination reactions? A: Usually a halide ion (-X). Q: What is the difference between SN1 and SN2 mechanisms? A: SN1 is unimolecular with carbocation intermediate; SN2 is bimolecular and concerted . Q: What is the difference between E1 and E2 mechanisms? A: E1 has carbocation intermediate; E2 is concerted with base abstracting proton and leaving group leaving simultaneously. ...

   💯 Nucleophilic Substitution Revision Q&A – Haloalkanes & Haloarenes (Class 12 Chemistry) Q: What is a nucleophilic substitution reaction ? A: A reaction in which a nucleophile replaces a leaving group , typically a halide, from an organic substrate. Q: Name two main mechanisms of nucleophilic substitution in haloalkanes . A: SN1 (unimolecular) and SN2 (bimolecular) mechanisms. Q: Which carbon hybridization is most favorable for nucleophilic substitution? A: sp 3 -hybridized carbon. Q: Why do haloarenes undergo nucleophilic substitution with difficulty? A: Due to resonance stabilization and partial double bond character in C–X bond. Q: What is the order of reactivity for SN2 mechanism: methyl, 1°, 2°, or 3° alkyl halides? A: Methyl > 1° > 2° > 3°. Q: What is the order of reactivity for SN1 mechanism: methyl, 1°, 2°, or 3° alkyl halides? A: 3° > 2° > 1° > methyl. Q: What determines the rate of SN1 reaction? A: Conc...

Short Answer Q&A – d- and f-block Elements (NCERT Class 12 Chemistry) Q: What are transition elements? A: Elements whose atoms or ions (in a stable oxidation state) contain partially filled d -orbitals. Q: Give the general outer electronic configuration of d-block elements. A: ( n -1) d 1–10 ns 1–2 . Q: Why are Zn, Cd, and Hg not considered true transition elements? A: They have completely filled d-orbitals ( d 10 ) in both atomic and common oxidation states (+2). Q: Why is Ag considered a transition element? A: It exhibits the +2 oxidation state (Ag 2+ ), with partially filled 4d 9 configuration. Q: Write the electronic configuration of Cr (Z=24). A: [Ar] 3d 5 4s 1 (Half-filled stability). Q: Write the electronic configuration of Cu (Z=29). A: [Ar] 3d 10 4s 1 (Fully-filled stability)...