ECAT Chemistry — Chemical Bonding

How Chemical Bonding is tested

Across the 7 ECAT past papers on ParhaiKrlo, Chemical Bonding accounts for 6 questions. It appears in 4 of them, about 1.5 questions a paper. The heaviest was ECAT Past Paper 05, with 2 questions, and the most recent is ECAT Past Paper 07, with 1.

Chemical Bonding MCQs from the ECAT past papers

Try each one before opening the answer. Each comes with a short explanation.

1. Q1 · ECAT Past Paper 07 · Chemical Bonding

   The structure of the nitrogen molecule (N₂) is explained by:

   • A.End-to-end overlap of orbitals forming a sigma bond and sideways overlap of other orbitals forming two pi bonds
   • B.End-to-end overlap forming one sigma bond and end-to-end overlap of other orbitals forming two pi bonds
   • C.One sigma bond and two pi bonds
   • D.Both options A and C are correct
   Show answer

   Answer: D. Both options A and C are correct — N≡N is one σ bond (head-on overlap) and two π bonds (sideways overlap).

2. Q2 · ECAT Past Paper 05 · Chemical Bonding

   In a microwave oven, the wave energy is absorbed by polar molecules. Which of the given substances would absorb the most energy?

   • A.SiO₂
   • B.C₂H₅OH
   • C.NaCl
   • D.None of these
   Show answer

   Answer: B. C₂H₅OH — Microwaves heat polar molecules that can rotate; ethanol is a polar liquid, while SiO₂ and NaCl are rigid solids.

3. Q3 · ECAT Past Paper 03 · Chemical Bonding

   The covalent bond length between two atoms can be determined experimentally by:

   • A.A microscope
   • B.A 'covalent meter'
   • C.Electron diffraction
   • D.All of the above
   Show answer

   Answer: C. Electron diffraction — Bond lengths are measured by diffraction (X-ray, electron) and spectroscopic methods, not microscopes.