`NaCl+" Solid" K_(2)Cr_(2)O_(7) + " Conc. H_(2)SO_(4) to "X"` (reddish brown fumes)
How many axial-d-orbital are involved in hybrization of "X" ?

Answer

To solve the question regarding the hybridization of the compound formed when NaCl reacts with K2Cr2O7 and concentrated H2SO4, leading to the formation of chromyl chloride (CrO2Cl2), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**:
- The reaction involves the heating of NaCl with solid K2Cr2O7 and concentrated H2SO4.
- The product formed is chromyl chloride (CrO2Cl2), which is responsible for the reddish-brown fumes.

2. **Determine the Oxidation State of Chromium**:
- In chromyl chloride (CrO2Cl2), we need to find the oxidation state of chromium (Cr).
- The formula can be analyzed as follows:
- Let the oxidation state of Cr be \( x \).
- The total charge from the two chloride ions (Cl) is -2 (since each Cl has a -1 charge).
- The two oxygen atoms (O) contribute -4 (since each O has a -2 charge).
- The overall charge of the compound is neutral (0).
- Therefore, the equation is:
\[ x + (-4) + (-2) = 0 \implies x - 6 = 0 \implies x = +6 \]
- Thus, the oxidation state of chromium in chromyl chloride is +6.

3. **Determine the Electronic Configuration of Chromium**:
- The electronic configuration of chromium in its elemental state is:
\[ \text{Cr: [Ar] 3d}^5 4s^1 \]
- In the +6 oxidation state, chromium loses 6 electrons:
\[ \text{Cr}^{+6}: \text{[Ar] 3d}^0 4s^0 \]
- This means that there are no electrons in the d orbitals.

4. **Identify the Hybridization**:
- The hybridization of a compound can be determined by the number of valence orbitals involved.
- In the case of CrO2Cl2, chromium has no d electrons available for hybridization, and the hybridization is determined by the surrounding atoms.
- The hybridization of CrO2Cl2 is typically \( sp^2 \) because it forms three sigma bonds (two with oxygen and one with chlorine).

5. **Count the Axial d Orbitals**:
- Since there are no d electrons available in the +6 oxidation state of chromium, the number of axial d orbitals involved in the hybridization is 0.

### Final Answer:
The number of axial d orbitals involved in the hybridization of chromyl chloride (X) is **0**.