The water-gas shift reaction \(\mathrm{CO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons\) \(\mathrm{CO}_{2}(g)+\mathrm{H}_{2}(g)\) is used industrially to produce hydrogen. The reaction enthalpy is \(\Delta H^{\circ}=-41 \mathrm{kJ}\) . (a) To increase the equilibrium yield of hydrogen would you use high or low temperature? ( b) Could you increase the equilibrium yield of hydrogen by controlling the pressure of this reaction? If so would high or low pressure favor formation of \(\mathrm{H}_{2}(g) ?\)

Le Chatelier's principle states that if a dynamic equilibrium system is subjected to some change, the system will adjust itself to minimize the effect of that change. In this case, the reaction is exothermic, which means it releases heat. An exothermic reaction can be represented as: \(\mathrm{CO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightleftharpoons \mathrm{CO}_{2}(g)+\mathrm{H}_{2}(g) + Heat\) To increase the equilibrium yield of hydrogen, we need to shift the equilibrium towards the products. According to Le Chatelier's principle, we should consider the following changes: 1. If we increase the temperature, the system will try to minimize the effect of increased heat by shifting the equilibrium towards the reactants (where heat is absorbed and less heat is produced). This would result in a lower yield of hydrogen. 2. If we decrease the temperature, the system will try to minimize the effect of decreased heat by shifting the equilibrium towards the products (where heat is released). This would result in a higher yield of hydrogen. So, to increase the equilibrium yield of hydrogen, we should use a low temperature.

To analyze the effect of pressure on equilibrium, we should look at the number of moles of gas on both sides of the reaction: Reactants: 1 mole CO + 1 mole H2O Products: 1 mole CO2 + 1 mole H2 The number of moles of gas on both sides of the reaction is equal. According to Le Chatelier's principle, changing the pressure will have no effect on the position of the equilibrium if there are no differences in the number of moles of gas between the reactants and products. So, we cannot increase the equilibrium yield of hydrogen by controlling the pressure in this reaction.