Which one of the following reactions represents water `-` gas shift reaction `?`

Options

A. `CO(g)+H_(2)O(g)underset("iron chormate")overset(673K)rarrCO_(2)+H_(2)`
B. `C(s)+H_(2)O(g)overset(1270K)rarrCO(g)+H_(2)`
C. `CH_(4)(g)+H_(2)O(g)underset(Ni)overset(1270K)rarrCO(g)+3H_(2)(g)`
D. None of these

Answer

To determine which reaction represents the water gas shift reaction, we need to understand what this reaction entails. The water gas shift reaction is a chemical reaction that involves the conversion of carbon monoxide (CO) and water (H2O) into carbon dioxide (CO2) and hydrogen gas (H2).

### Step-by-Step Solution:

1. **Identify the Water Gas Shift Reaction:**
The water gas shift reaction can be represented by the following equation:
\[ \text{CO} + \text{H}_2\text{O} \rightleftharpoons \text{CO}_2 + \text{H}_2 \]
This reaction shows that carbon monoxide reacts with water to produce carbon dioxide and hydrogen gas.

2. **Analyze the Given Options:**
You need to look at the options provided in the question and identify which one matches the above equation.

3. **Select the Correct Reaction:**
Among the options, you should find the reaction that shows the conversion of CO and H2O into CO2 and H2. The correct representation of the water gas shift reaction is:
\[ \text{CO} + \text{H}_2 \rightarrow \text{CO}_2 + \text{H}_2 \]
This indicates that carbon monoxide and hydrogen gas react to form carbon dioxide and hydrogen gas.

4. **Confirm the Reaction Conditions:**
The water gas shift reaction typically occurs in the presence of a catalyst (like Fe2O3 or Cr2O3) at elevated temperatures (around 673 K).

5. **Conclude the Correct Answer:**
Based on the analysis, the correct answer to the question is the reaction:
\[ \text{CO} + \text{H}_2 \rightarrow \text{CO}_2 + \text{H}_2 \]
Therefore, the correct option is the first one.