Which of the following statements is correct

Options

A. oxidation number of Fe in `[Fe(H_(2)O)_(5)NO]SO_(4)` is +1
B. oxidation number of sodium in sodium amalgam is -1
C. oxidation state of carbon in HCN is + 4
D. All statement are correct

Explanation

To determine which of the statements is correct, we need to analyze each statement regarding oxidation states and the compounds mentioned.

### Step-by-Step Solution:

1. **Analyzing the first statement regarding the complex FeH2, Hol5, NO, SO4:**
- We need to find the oxidation state of iron (Fe) in this complex.
- Let the oxidation state of Fe be \( x \).
- The ligands (H2, Hol5, NO, SO4) have the following charges:
- H2 is neutral (0 charge).
- Hol5 is neutral (0 charge).
- NO is +1 (as it is a nitrosyl ligand).
- SO4 is -2 (sulfate ion).
- The overall charge of the complex is 0.
- Therefore, we can set up the equation:
\[ x + 0 + 1 - 2 = 0 \]
Simplifying gives:
\[ x - 1 = 0 \implies x = +1 \]
- Thus, the oxidation state of iron in this complex is +1. This statement is **correct**.

2. **Analyzing the second statement regarding sodium in sodium amalgam (NaHg):**
- Sodium amalgam is a mixture of sodium and mercury, not a compound.
- In sodium amalgam, sodium does not undergo a change in oxidation state due to the lack of a chemical bond formation.
- Therefore, the oxidation state of sodium in sodium amalgam is 0, not -1. This statement is **false**.

3. **Analyzing the third statement regarding the oxidation state of carbon in HCN:**
- In HCN, we need to determine the oxidation state of carbon.
- Hydrogen (H) is usually +1, and nitrogen (N) is more electronegative than carbon.
- Let the oxidation state of carbon be \( y \).
- The equation based on the oxidation states is:
\[ +1 + y + (-3) = 0 \]
Simplifying gives:
\[ y - 2 = 0 \implies y = +2 \]
- Thus, the oxidation state of carbon in HCN is +2, not +3 or +4. This statement is **false**.

### Conclusion:
The only correct statement is the first one regarding the oxidation state of iron in the complex FeH2, Hol5, NO, SO4, which is +1.