Q.Give the uses of helium.

Helium's chemical inertness, low density, and extremely low boiling point make it useful for airships/balloons, deep-sea diving gas mixtures, inert atmospheres for welding, and as the standard cryogenic coolant for superconducting magnets.

Uses of helium: (i) Balloons and airships: being much lighter than air and completely non-flammable (unlike hydrogen), helium is the safe choice for filling weather balloons and airships.

(ii) Deep-sea diving: helium is mixed with oxygen (a mixture called 'heliox') for deep-sea divers, replacing nitrogen; this avoids nitrogen narcosis at depth and reduces the risk of decompression sickness ('the bends') on ascent, since helium is much less soluble in blood/fatty tissue than nitrogen.

(iii) Inert atmosphere for welding: helium (along with argon) is used to provide an inert, non-reactive shielding atmosphere in arc welding of metals, preventing oxidation of the hot metal. …