`CO` on passing over heated nickel gives

Options

A. `Ni(CO)_(4)`
B. `NiCO_(3)`
C. `CO + H_(2)`
D. `CO_(2)+H_(2)`

Explanation

To solve the question "CO on passing over heated nickel gives," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this reaction are carbon monoxide (CO) and nickel (Ni).

2. **Understand the Conditions**: The reaction occurs when carbon monoxide is passed over heated nickel. The temperature is typically high, around 80 degrees Celsius or more.

3. **Determine the Product**: When carbon monoxide reacts with heated nickel, it forms nickel tetracarbonyl (Ni(CO)₄). This is a complex compound where nickel is coordinated with four carbon monoxide molecules.

4. **Write the Chemical Equation**: The reaction can be represented as:
\[ \text{Ni} + 4 \text{CO} \rightarrow \text{Ni(CO)}_4 \]
Here, nickel is in the zero oxidation state in nickel tetracarbonyl.

5. **Identify the Nature of the Product**: Nickel tetracarbonyl is a gaseous compound at room temperature, and it is an example of metal carbonyls, which are complexes formed between metals and carbon monoxide.

6. **Conclusion**: Therefore, the final answer to the question is that carbon monoxide (CO) on passing over heated nickel gives nickel tetracarbonyl (Ni(CO)₄).