Hydrogen chloride is a polar covalent bond because the shared electron pair is unequally shared due to the higher electronegativity of chlorine (3.0) compared to hydrogen (2.1). The bond has a dipole moment, making HCl molecule polar. In water, HCl ionizes to H⁺ and Cl⁻, but the gaseous molecule is covalent. Pure ionic bonds exist in compounds like NaCl where electronegativity difference is large (>1.7).
Explanation:
SO₂ from burning coal and NOₓ from vehicles form H₂SO₄ and HNO₃ in rain. CO₂ forms weak carbonic acid (normal rain pH ~5.6). Ammonia is basic and neutralizes acidity.
Explanation:
Mg goes from 0 to +2 oxidation state, losing electrons – oxidized. Oxygen is reduced (0 to -2). This is a combustion/combination redox reaction.
Explanation:
Isobars are atoms of different elements with the same mass number but different atomic numbers. ⁴⁰Ar (atomic number 18) and ⁴⁰Ca (atomic number 20) both have mass number 40. Options A and D are isotopes (same element, different mass number). Option C are isotopes of hydrogen. Isobars have different chemical properties because of different proton numbers. Example: ¹⁴C and ¹⁴N.
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