Problem 42 - Chemistry An Atoms First Approach

Question

The reaction $$\mathrm{SO}_{3}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}(a q) $$ is the last step in the commercial production of sulfuric acid. The enthalpy change for this reaction is \(-227 \mathrm{kJ}\). In designing a sulfuric acid plant, is it necessary to provide for heating or cooling of the reaction mixture? Explain.

Step-by-Step Solution

Answer

In designing a sulfuric acid plant, it is necessary to provide for cooling of the reaction mixture because the given reaction has a negative enthalpy change of -227 kJ, indicating that it is exothermic. This means heat is released during the reaction, potentially raising the temperature of the mixture beyond desired levels.

Step 1: Identify the enthalpy change of the reaction

The given enthalpy change for the reaction is -227 kJ.

Step 2: Analyze the enthalpy change

Since the enthalpy change is negative, this reaction is exothermic. In an exothermic reaction, heat is released as the reaction proceeds, raising the temperature of the reaction mixture.

Step 3: Determine the need for heating or cooling

In an exothermic reaction, the released heat increases the temperature of the mixture. Therefore, to control the temperature and maintain the desired levels, it may be necessary to provide cooling for the reaction mixture in the sulfuric acid plant.

Step 4: Conclusion

In designing a sulfuric acid plant, it is necessary to provide for cooling of the reaction mixture since the reaction is exothermic, and the temperature may rise beyond the desired levels.

Key Concepts

Exothermic Reaction

An exothermic reaction is a chemical process that releases energy, usually in the form of heat. This is indicated by a negative enthalpy change (\(-\Delta H\)). Such reactions occur when the energy needed to start the reaction is less than the energy released after the reaction is complete.
This means that the products of the reaction are more stable than the reactants because they have less energy.
For the reaction of sulfur trioxide (\( \text{SO}_3 \)) with water (\( \text{H}_2\text{O} \)) to form sulfuric acid (\( \text{H}_2\text{SO}_4 \)), the enthalpy change is -227 kJ.
This significant negative value confirms that the reaction is exothermic.
Exothermic reactions are commonly used in industrial applications, such as heating devices or chemical plants, because they can efficiently produce energy. However, they also require careful temperature management to prevent overheating and ensure safety.

Sulfuric Acid Production

Sulfuric acid (\( \text{H}_2\text{SO}_4 \)) is a highly important industrial chemical with a variety of uses. It is used in the production of fertilizers, chemicals, and petroleum refining, among others.
The commercial production of sulfuric acid typically involves several steps, but the reaction forming \( \text{H}_2\text{SO}_4 \) from sulfur trioxide and water is the final critical step.

• Initial steps often include the oxidation of sulfur (\( \text{S} \)) to form sulfur dioxide (\( \text{SO}_2 \)).
• Sulfur dioxide is then further oxidized to sulfur trioxide (\( \text{SO}_3 \)).
• The \( \text{SO}_3 \) is subsequently reacted with water to produce sulfuric acid.

This process must be controlled precisely to ensure high yields and prevent any safety hazards. The exothermic nature of the final step means it generates significant heat, contributing to the overall energy efficiency of the process when properly managed.

Reaction Temperature Control

Controlling reaction temperature is crucial in industrial chemical productions like sulfuric acid production. Exothermic reactions like the one forming sulfuric acid can rapidly increase in temperature, affecting both the safety and efficiency of the process.
When designing facilities for sulfuric acid production, including systems for cooling and temperature regulation is essential. Excessive heat can lead to:

• Reduced yields due to undesired side reactions.
• Potential equipment damage or failure due to overheating.
• Risk to workers and the environment if the reaction isn't contained properly.

To manage these risks, cooling systems are often installed. These may include heat exchangers or chilled water systems, allowing the reaction to proceed at an optimal temperature. The goal is to maintain a steady state where the amount of heat produced matches the heat removed, ensuring continuous production without interruptions.