.............. is used as a catalyst in Bosch process.

Answer

**Step-by-Step Solution:**

1. **Understand the Concept of a Catalyst:**
- A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It helps the reactants to convert into products more efficiently.

2. **Identify the Bosch Process:**
- The Bosch process is a method used to produce hydrogen gas. It involves a reaction between carbon monoxide (CO) and hydrogen (H2).

3. **Know the Reaction in the Bosch Process:**
- The reaction can be summarized as follows:
\[ \text{CO} + \text{H}_2 \text{ (water gas)} \xrightarrow{\text{catalyst}} \text{CO}_2 + \text{H}_2 \]
- In this process, carbon monoxide reacts with steam (water) to produce carbon dioxide and hydrogen gas.

4. **Identify the Catalysts Used:**
- The catalysts used in the Bosch process are iron oxide (Fe2O3) and chromium oxide (Cr2O3). These catalysts facilitate the reaction without being consumed.

5. **Conclusion:**
- Therefore, the catalysts used in the Bosch process are **iron oxide and chromium oxide**.

**Final Answer:** Iron oxide and chromium oxide are used as catalysts in the Bosch process.

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