Sulfuric acid is manufactured industrially by a four-step process as shown:
Step 1: Sulfur is burned in excess air to produce sulfur dioxide.
Step 2: Sulfur dioxide is converted into sulfur trioxide.
Step 3: Sulfur trioxide is reacted with concentrated sulfuric acid to produce Substance Y.
Step 4: Substance Y is reacted with water to produce concentrated sulfuric acid.
(a) (i) Name the process used in the industrial manufacture of sulfuric acid.
(ii) Identify substance Y produced in Step 3.
(b) By writing the balanced chemical equation, describe how sulfur dioxide is converted into sulfur trioxide in Step 2.
Answer (2)
The industrial manufacture of sulfuric acid uses the Contact Process. In Step 3, the substance produced is oleum. The conversion of sulfur dioxide to sulfur trioxide is represented by the equation: 2 SO₂ + O₂ ↔ 2 SO₃, using a catalyst like vanadium(V) oxide.
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Contact Process Overview: This is the principal method of manufacturing sulfuric acid in high concentrations needed for industrial purposes. It involves several important reactions and requires catalysts and controlled conditions.
Step 1: Combustion of sulfur to form sulfur dioxide as a gas. This step ensures the availability of sulfur dioxide in large quantities.
Step 2 (Detailed):
Catalyst: Vanadium(V) oxide is used to increase the rate of reaction without being consumed in the process.
Temperature: The temperature range of 400°C to 600°C is optimal for converting SO₂ to SO₃ efficiently.
Exothermic Reaction: The reaction releases heat, which is why controlling the temperature is important to ensure efficiency and safety.
Step 3: Sulfur trioxide is absorbed into concentrated sulfuric acid to form oleum, which offers a method to handle SO₃ before it is diluted in water to form additional sulfuric acid.
Step 4: Oleum is carefully reacted with water to produce concentrated sulfuric acid, concluding the process and making the acid available for various industrial applications.
