Q.(a)
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(a) The empirical formula is C6H6O and Pauli's principle forbids two electrons having identical quantum numbers; (b) Be and Al show a diagonal relationship (amphoteric oxides, covalent chlorides, solubility in alkali, passivity to conc. HNO3).
PART (a)(i) — Empirical formula from 76.6% C, 6.38% H, 17.02% O:
Divide each percentage by its atomic mass to get relative moles:
- C: 76.6 / 12 = 6.38
- H: 6.38 / 1 = 6.38
- O: 17.02 / 16 = 1.06 Divide each by the smallest value (1.06):
- C: 6.38 / 1.06 = 6.0
- H: 6.38 / 1.06 = 6.0
- O: 1.06 / 1.06 = 1.0 So C : H : O = 6 : 6 : 1, and the empirical formula is C6H6O.
PART (a)(ii) — Pauli Exclusion Principle:
"No two electrons in the same atom can have the same set of all four quantum numbers (n, l, m, s)." As a consequence, an orbital (fixed n, l, m) can hold at most two electrons, and these must have opposite spins.
PART (b) — Similarities between Beryllium and Aluminium (diagonal relationship):
- Both form amphoteric oxides and hydroxides (BeO, Be(OH)2 and Al2O3, Al(OH)3) that dissolve in both acids and alkalis.
- Both dissolve in strong alkali forming beryllate and aluminate ions, liberating hydrogen.
- Their chlorides (BeCl2 and AlCl3) are covalent, exist as polymeric/dimeric bridged structures, are soluble in organic solvents and act as Lewis acids (catalysts). …
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