Q.How does the atomic hydrogen or oxy-hydrogen torch function for cutting and welding purposes ? Explain.

Atomic hydrogen torch: Two tungsten electrodes are maintained under a stream of hydrogen gas, and an electric arc is struck between them. The arc supplies enough energy to dissociate dihydrogen molecules into free hydrogen atoms:

This is a highly endothermic process — a large amount of energy is stored in the free atoms.

When this stream of atomic hydrogen is directed onto a metal surface to be welded/cut, the highly reactive H atoms recombine to reform stable H2 molecules right at that surface:

This recombination releases the previously absorbed energy instantaneously and locally as intense heat — temperatures of roughly 4000 K can be achieved, sufficient to melt/fuse metals for welding or to cut through them.

Oxy-hydrogen torch: works on a related but simpler principle — dihydrogen gas is simply combusted with oxygen gas:

$2H_2(g) + O_2(g) \rightarrow 2H_2O(g) \qquad \Delta H < 0$ …

Trace the energy cycle for the atomic torch: dissociation of H2 into atoms absorbs energy at the arc, recombination at the workpiece releases it as heat; co …

• Describing the atomic hydrogen torch as simply "burning hydrogen" — its mechanism is dissociation-then-recombination, not combustion with oxygen. …