Which of the following reactiona is an example of use of water gas in the synthesis of other compounds?

Options

A. `CH_(4)(g)+H_(2)O(g)underset(Ni)overset(1270K)rarrCO(g)+H_(2)(g)`
B. `CO(g) +H_(2)O(g) underset("Catalyst")overset(673K)to CO_(2)(g) + H_(2)(g)`
C. `C_(n)H_(2n) +._(2)+nH_(2)O(g) underset(Ni)overset(1270K)to nCO+ (2n + 1)H_(2)`
D. `CO(g) + 2H_(2)(g)underset("Catalyst")overset("Cobalt")to CH_(3)OH(l)`

Explanation

To solve the question regarding which reaction is an example of the use of water gas in the synthesis of other compounds, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Water Gas**:
- Water gas, also known as synthesis gas or syngas, is a mixture of carbon monoxide (CO) and hydrogen (H₂). It is produced by the reaction of steam with carbon-containing materials.

2. **Identifying the Application of Water Gas**:
- One of the primary applications of water gas is in the synthesis of methanol. Methanol (CH₃OH) is an important chemical used in various industrial processes.

3. **The Reaction for Methanol Synthesis**:
- The chemical reaction for synthesizing methanol from water gas can be represented as:
\[ \text{CO} + 2\text{H}_2 \xrightarrow{\text{Cobalt catalyst}} \text{CH}_3\text{OH} \]
- In this reaction, one molecule of carbon monoxide reacts with two molecules of hydrogen in the presence of a cobalt catalyst to produce one molecule of methanol.

4. **Analyzing the Options**:
- Given multiple options, we need to identify which one corresponds to the above reaction. The correct option will show carbon monoxide and hydrogen reacting to form methanol.

5. **Conclusion**:
- After comparing the options, the correct answer is the one that represents the reaction of carbon monoxide and hydrogen to form methanol, which is option 4.

### Final Answer:
The reaction that is an example of the use of water gas in the synthesis of other compounds is:
**Option 4: CO + 2H₂ → CH₃OH (in presence of cobalt catalyst)**