Water gas is mixed with steam and the mixture is passed over heated `Fe_(2) O_(3)` in presence of `Cr_(2)O_(3)`. The mixture when passed in water dissolves `CO_(2)` and dihydrogen left undissolved is collected . This method of preparation of hydrogen gas is know as

Options

A. Bosch process
B. Lane process
C. Kellner process
D. Hall process

Answer

To solve the question regarding the method of preparation of hydrogen gas from water gas mixed with steam and passed over heated Fe₂O₃ in the presence of Cr₂O₃, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Water Gas**: Water gas is a mixture of carbon monoxide (CO) and hydrogen (H₂). It is produced by passing steam over hot carbon (coke).

2. **Mixing with Steam**: In this process, water gas (CO + H₂) is mixed with steam (H₂O). The steam provides additional water molecules that will react with the carbon monoxide.

3. **Catalytic Reaction**: The mixture of water gas and steam is then passed over heated iron(III) oxide (Fe₂O₃) in the presence of chromium(III) oxide (Cr₂O₃). Here, Fe₂O₃ acts as a catalyst, and Cr₂O₃ acts as a promoter to enhance the reaction.

4. **Chemical Reaction**: The reaction that occurs can be represented as follows:
\[ CO + H_2O \xrightarrow{Fe_2O_3, Cr_2O_3} CO_2 + H_2 \]
This reaction converts carbon monoxide and steam into carbon dioxide (CO₂) and hydrogen gas (H₂).

5. **Separation of Gases**: After the reaction, the mixture contains carbon dioxide and hydrogen. When this mixture is passed through water, carbon dioxide dissolves in water, while hydrogen remains undissolved.

6. **Collection of Hydrogen**: The undissolved hydrogen gas is then collected, as it does not react with water and can be easily separated.

7. **Naming the Process**: This method of preparing hydrogen gas from water gas and steam is known as the "Water Gas Shift Reaction" or more commonly referred to as the "Water Gas Process" or "Watt's Process".

### Final Answer:
The method of preparation of hydrogen gas described in the question is known as the **Water Gas Process**.