Give reasons for:
(i) Ozone is more reactive than oxygen.
(ii) An acidified K2Cr2O7 paper on being exposed to SO2 turns green.
(iii) Sulphuric acid never acts as a reducing agent.
(iv) Noble gases are mostly chemically inert.
(v) Nitrogen is fairly inert.
(i)
Ozone is a powerful oxidizing agent and oxidation with ozone evolves more heat and usually starts at a lower temperature than oxidation with oxygen. It reacts with non-saturated organic compounds to produce ozonides, which are unstable and may decompose with explosive violence. Ozone is an unstable gas which, at normal temperatures, decomposes to diatomic oxygen. At elevated temperatures and in the presence of certain catalysts such as hydrogen, iron, copper and chromium, this decomposition may be explosive.
ii) When SO2 gas is passed through acidified potassium dicromate solution the orange colour potassium dichromate disappear and green colour ofchomium sulphate appears.
3SO2 +K2Cr2O7 +H2SO4 ----> K2SO4 +Cr2(SO4)3green colour +H2O
iii) The concentrated sulphuric acid can act both as an acid and as an oxidising agent. The concentrated sulphuric acid gives a hydrogen ion to the halide ion to produce a hydrogen halide. Because this is a gas, it immediately escapes from the system sulphuric acid ionises in two steps.
H2SO4(aq) + H2O(l) → H3O+(aq) + HSO4–(aq)
Ka1 = very large (Ka1 >10)
HSO4–(aq) + H2O(l) → H3O+(aq) + SO42-(aq)
Ka2 = 1.2 × 10–2
The larger value of
Ka1 (Ka1 >10) means that H2SO4 is largely
dissociated into H+ and HSO4–. Greater the value of dissociation constant(Ka), the stronger is the acid.
iv)Noble gases are inert because electronic configuration of noble gas is ns2 np6 they contain a 'stable octet' of electrons in the outermost shell of the atom (valence electrons). This means that the noble gases do not need to react to lose or gain electrons in order to become stable, since scientists have determined that 8 valence electrons is a stable electron configuration.
v) Nitrogen is small in size and nitrogen has unique ability to form pπ -pπ multiple bonds with itself and with other elements having small size and high electronegativity (e.g., C, O).
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