In a `20` litre vessel initially each have `1-1` mole. `CO,H_(2)OCO_(2)` is present, then for the equilibrium of `CO+H_(2)OhArrCO_(2)+H_(2)` following is true:

Options

A. `H_(2)`, more then `1` mole
B. `CO,H_(2)O,H_(2)` less then `1` mole
C. `CO_(2) "&" H_(2)O` both more then `1` mole
D. All of these

Explanation

To solve the problem step by step, let's analyze the equilibrium reaction and the initial conditions provided.

### Step 1: Write the Balanced Chemical Equation
The reaction given is:
\[ \text{CO} + \text{H}_2\text{O} \rightleftharpoons \text{CO}_2 + \text{H}_2 \]

### Step 2: Identify Initial Conditions
We are given that in a 20-liter vessel:
- Initial moles of CO = 1 mole
- Initial moles of H2O = 1 mole
- Initial moles of CO2 = 1 mole
- Initial moles of H2 = 0 moles

### Step 3: Set Up the ICE Table
We can set up an ICE (Initial, Change, Equilibrium) table to track the changes in concentration as the system reaches equilibrium.

| Species | Initial (moles) | Change (moles) | Equilibrium (moles) |
|------------|------------------|----------------|----------------------|
| CO | 1 | -x | 1 - x |
| H2O | 1 | -x | 1 - x |
| CO2 | 1 | +x | 1 + x |
| H2 | 0 | +x | 0 + x = x |

### Step 4: Analyze the Changes
At equilibrium:
- The moles of CO and H2O will decrease by \( x \).
- The moles of CO2 and H2 will increase by \( x \).

### Step 5: Determine the Value of x
Since the reaction does not go to completion, \( x \) must be less than 1 mole. Therefore:
- \( 1 - x > 0 \) implies \( x < 1 \)
- \( 1 + x > 1 \) implies \( x > 0 \)

### Step 6: Evaluate Each Statement
Now, let’s evaluate the statements provided in the question:

1. **H2 is more than 1 mole**: This is incorrect because at equilibrium, \( H2 = x \) and since \( x < 1 \), \( H2 < 1 \).

2. **CO is less than 1 mole**: This is correct because \( CO = 1 - x \) and since \( x > 0 \), \( CO < 1 \).

3. **H2 is less than 1 mole**: This is also correct because \( H2 = x \) and since \( x < 1 \), \( H2 < 1 \).

4. **CO2 and H2O both more than 1 mole**: This is incorrect because \( CO2 = 1 + x \) (which is more than 1) and \( H2O = 1 - x \) (which is less than 1).

### Conclusion
The only correct statement is that CO is less than 1 mole. Therefore, the correct answer is option B.