In contact process, the catalyst used in the conversion of sulphur(IV)oxide to sulphur(VI) oxide is

1. Analyze the Question

The question asks for the specific catalyst used in the Contact Process to convert sulphur(IV) oxide ($SO_2$) into sulphur(VI) oxide ($SO_3$). This is a critical step in the industrial manufacture of sulphuric acid.

2. Explain the Concept

The Contact Process involves the catalytic oxidation of sulphur(IV) oxide. The reaction is represented by the equation:

To make this reaction proceed at a reasonable rate and yield, a catalyst is required. While platinum was historically used, it is very expensive and easily "poisoned" (rendered inactive) by impurities like arsenic. Therefore, modern industrial processes use vanadium(V) oxide ($V_2O_5$) because it is cheaper, more durable, and highly effective.

3. Show the Solution

• Step 1: Identify the reaction: $2SO_2 + O_2 \rightarrow 2SO_3$.
• Step 2: Evaluate the options: • Nickel: Used in the hydrogenation of oils (hardening of fats). • Platinum: Historically used, but replaced by vanadium(V) oxide due to cost and sensitivity to poisoning. • Vanadium(V) oxide ($V_2O_5$): The standard industrial catalyst for the Contact Process. • Magnesium(IV) oxide: This is not a standard catalyst for this process (and is chemically unstable in this form).
• Step 3: Conclusion: Vanadium(V) oxide is the correct catalyst used in the modern Contact Process.

4. Identify the Answer

The correct option is C.

5. Exam Tip

When studying industrial processes for Chemistry, always distinguish between the catalyst and the conditions. For the Contact Process, remember:

• Catalyst: Vanadium(V) oxide ($V_2O_5$).
• Temperature: About 450°C (a compromise temperature).
• Pressure: 1–2 atmospheres.