Write structures of :(i) Chlorous acid(ii) Perchloric acid(b) Write uses of Helium

Answer:

(a) (i) Chlorous acid, HClO₂: H–O–Cl=O (Cl bonded to one –OH and one =O; two lone pairs on Cl; bent shape).

(ii) Perchloric acid, HClO₄: Cl at the centre of a tetrahedron, bonded to one –OH group and three =O atoms: H–O–Cl(=O)₃.

(b) Uses of helium:

• Being light and non-inflammable, it is used to fill balloons and airships (e.g. weather balloons).
• A mixture of helium and oxygen is used by deep-sea divers for breathing, since helium is much less soluble in blood than nitrogen (prevents ‘bends’), and in treatment of asthma.
• Liquid helium is used as a cryogenic agent for very low temperature work, e.g. cooling superconducting magnets in MRI machines.
• It provides an inert atmosphere in welding and in growing silicon/germanium crystals, and is used in gas-cooled nuclear reactors.