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

Explanation

(i) In an atomic hydrogen torch, an electric arc is struck between tungsten electrodes in an atmosphere of molecular hydrogen (Fig. a). The energy of the arc is sufficient to dissociate `H_(2)` molecules into H atoms as shown below.
`H_(2)(g)underset(2270K)overset("Electric arc")to2H,DeltaH=+435.9kJmol^(-1)`

The life time of atomic hydrogen is only 0.3 seconds. Therefore, H atoms formed as above immediately combine together to form `H_(2)` molecules with the liberation of large amount of energy and thus producing high temperatures (4300-5300 K). The high energy released is used for cutting and welding purposes. Additional advantage of using this torch is that the metal does not get oxidised due to the presence of an atmosphere of hydrogen.
(ii) In oxy-hydrogen torch, dihydrogen gas is burnt in an atmosphere of oxygen producing an intensely hot flame (Fig. b). This torch is used for cutting and welding purposes.