36. Sulphuric acid: Preparation: By contact process
18 S8 + O2 → SO2
Exothermic reaction and therefore low temperature and high pressure are favourable
SO3( g) + H2 SO4 → H2 S2 O7( Oleum)
H2S2O7 + H2O → 2 H2SO4( 96 − 98 %)
It is dibasic acid or diprotic acid.
It is a strong dehydrating agent.
It is a moderately strong oxidizing agent.
GROUP 17 ELEMENTS
37. Atomic and ionic radii: Halogens have the smallest atomic radii in their respective periods because of maximum effective nuclear charge.
38. Ionisation enthalpy: They have very high ionization enthalpy because of small size as compared to other groups.