Final answer:
Water is not added directly to sulfur trioxide in the Contact process due to the highly exothermic nature of the reaction, leading to the formation of a corrosive mist.option b) The reaction is highly exothermic, leading to the formation of a corrosive mist.
Step-by-step explanation:
In the Contact process for manufacturing sulfuric acid, water is not added directly to sulfur trioxide (SO3) because the reaction between water and sulfur trioxide is highly exothermic, which can lead to the formation of a corrosive mist as the correct answer is option b).
When SO3 reacts with water (H2O), it forms sulfuric acid (H2SO4). The direct combination of sulfur trioxide with water releases a significant amount of energy in the form of heat, causing the solution to vaporize and form a corrosive mist that is difficult to contain and can be dangerous to both the equipment and the operators. To avoid these hazards, sulfur trioxide is first dissolved in concentrated sulfuric acid to form oleum, which can then be safely diluted with water to produce sulfuric acid.