Given below are two reactions, involved in the commercial production of dihydrogen (H$_2$). The two reactions are carried out at temperature "T$_1$" and "T$_2$", respectively

$C(s) + {H_2}O(g)\buildrel {{T_1}} \over \longrightarrow CO(g) + {H_2}(g)$

$$CO(g) + {H_2}O(g)\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{Catalyst}^{{T_2}}} C{O_2}(g) + {H_2}(g)$$

The temperatures T$_1$ and T$_2$ are correctly related as :

<p>These reactions are part of the water-gas shift reaction used in the industrial production of hydrogen. The first reaction is the endothermic steam reforming of coal (carbon), while the second reaction is the exothermic water-gas shift reaction.</p> <ol> <li><p>Carbon reacts with steam at high temperatures (around 1000°C or 1273 K) to form carbon monoxide and hydrogen:<br/><br/> C(s) + H$_2$O(g) $\xrightarrow[T_1]{}$ CO(g) + H$_2$(g)</p> </li><br/> <li><p>Then carbon monoxide reacts with steam in the presence of a catalyst to produce carbon dioxide and more hydrogen:<br/><br/> CO(g) + H$_2$O(g) $\xrightarrow[Catalyst]{[T_2]}$ CO$_2$(g) + H$_2$(g)</p> </li> </ol> <p>Since the first reaction is endothermic (absorbs heat), it requires a higher temperature to proceed than the second reaction, which is exothermic (releases heat). Therefore, the temperature T$_1$ should be higher than T$_2$.</p>