A. (i) Ozone is thermodynamically unstable because it decomposes into O2 with the evolution of heat i.e. ΔH is negative. Also, since the decomposition of O3 increases the number and freedom of particles, entropy also increases.
We know that, ΔG = ΔH – TΔS
Both – ΔH and -TΔS result into large negative ΔG. Hence O3 becomes thermodynamically unstable.
(ii) Solid PCl5 is ionic in nature because it exists as [PCl4]+ [PCl6]- in which the cation has tetrahedral geometry and the anion has octahedral geometry.
(iii) Fluorine forms only one oxoacid HoF because of its small size and high electronegativity.
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