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Commercial Use of Enthalpy


The reaction between chlorine gas and phosphorus trihydride gas to create phosphorous trichloride gas and hydrogen chloride gas is exothermic in nature ($ΔH_{rxn}$= -570 kJ/mol).

When the reaction is carried out in a rigid vessel, which of the following BEST describes the commercial considerations in a processing plant?


The reaction vessel must be emptied of all gas at regular intervals and properly cleaned to ensure the pressure does not exceed the capacity of the reaction chamber and no contamination is present.


The reaction vessel must be cooled by an external source to ensure excess heat does not cause over-expansion of the gases, resulting in stress cracks in the reaction vessel.


The reaction vessel must be cooled by an external source to below the boiling point of the phosphorus trihydride gas in order to easily remove product and to reduce the overall heat produced during the reaction.


Nothing needs to be done since all the reactants and products are in the gas phase, and the reaction vessel should be able to withstand any amount of pressure and heat.