Which is not a method of preparing carbon monoxide on a commercial scale?

Options

A. `C_(S) + H_(2) O_((g)) overset(473 - 1273 K)(to) CO_((g)) + H_(2(g))`
B. `2C_((s)) + O_(2(g)) + 4N_(2(g)) overset(1273 K)(to) 2CO_((g)) + 4N_(2(g))`
C. `2C_((s)) + O_(2(g)) overset(Delta)(to) 2CO_((g))`
D. `HCOOH underset(conc.H_(2)SO_(4))overset(373 K)(to) H_(2)O + CO`

Explanation

To determine which method is not used for preparing carbon monoxide on a commercial scale, we will evaluate the common methods of carbon monoxide production and identify the one that is not suitable for large-scale production.

### Step-by-Step Solution:

1. **Identify Common Methods of Carbon Monoxide Production:**
- Carbon monoxide (CO) can be produced through several methods, including:
- Partial oxidation of hydrocarbons.
- Gasification of coal.
- Reforming of natural gas.
- Decomposition of formic acid.

2. **Evaluate Each Method:**
- **Partial Oxidation of Hydrocarbons:** This method is widely used in industries to produce carbon monoxide and hydrogen. It is efficient and suitable for large-scale production.
- **Gasification of Coal:** This is a common commercial method where coal is converted into gas, producing carbon monoxide along with other gases.
- **Reforming of Natural Gas:** This method involves reacting natural gas with steam or air to produce carbon monoxide and hydrogen, and is also used on a commercial scale.
- **Decomposition of Formic Acid:** When heated, formic acid decomposes to produce carbon monoxide and water. However, this method is generally not used on a commercial scale due to several limitations.

3. **Analyze the Limitations of Formic Acid:**
- **High Energy Requirement:** The process requires significant energy input for heating.
- **Slower Reaction Rate:** The reaction does not proceed as quickly as other methods.
- **Undesirable By-products:** The decomposition may yield by-products that are not useful.
- **High Cost of Investment:** The overall cost of using formic acid is higher compared to other methods.

4. **Conclusion:**
- Based on the analysis, the method of preparing carbon monoxide using formic acid is not suitable for commercial-scale production. Therefore, the answer to the question is that using formic acid is not a method of preparing carbon monoxide on a commercial scale.

### Final Answer:
The method that is not used for preparing carbon monoxide on a commercial scale is **using formic acid (HCOOH)**.

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