Nitrogen , oxygen and fluorine are the highly electronegative elements. When they are tied to a hydrogen atom to form covalent bond, the electrons of the covalent bond are shifted towards the more electronegative atom.This partially positively charged hydrogen atom forms a bond with the other electronegative atom. This bond is called as hydrogen bond and is weaker than covalent bond.For example, in HF molecule, the hydrogen bond exists between hydrogen atom of one molecule and fluorine atom of another molecule as depicted
`---H^(delta+)-F^(delta-)---H^(delta+)-F^(delta-)---H^(delta+)-F^(delta-)`
Here, hydrogen bond acts as bridge between atoms which holds one atom by covalent bond and the other by hydrogen bond.Hydrogen bond is represented by a dotted line (---) while a solid line represents the covalent bond. Thus, hydrogen bond can be defined as the attractive force which binds hydrogen atom of one molecule with the electronegative atom (F,O and N) of another molecule.
If boiling point of ortho-nitro phenol and para nitro phenol are `t_1 and t_2` respectively and mixture of these two are heated at temperature 't' where 't' is between these two temperature.Vapours will significantly contains

Options

A. Ortho nitro phenol
B. Para nitro phenol
C. Both ortho and para nitro phenol
D. None of these

Explanation

To solve the problem regarding the vapor composition of a mixture of ortho-nitrophenol and para-nitrophenol when heated at a temperature \( t \) between their boiling points \( t_1 \) and \( t_2 \), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structures**:
- Ortho-nitrophenol has the hydroxyl (-OH) group and the nitro (-NO2) group on adjacent carbon atoms, which allows for intramolecular hydrogen bonding.
- Para-nitrophenol has the -OH and -NO2 groups on opposite sides of the benzene ring, allowing for intermolecular hydrogen bonding.

2. **Identify the Type of Hydrogen Bonding**:
- In ortho-nitrophenol, the intramolecular hydrogen bonding reduces the ability of the molecules to interact with each other, which lowers the boiling point.
- In para-nitrophenol, the intermolecular hydrogen bonding allows for stronger interactions between molecules, leading to a higher boiling point.

3. **Analyze the Boiling Points**:
- Since boiling point is directly related to the strength of hydrogen bonding, para-nitrophenol, with its stronger intermolecular hydrogen bonding, will have a higher boiling point \( t_2 \) compared to ortho-nitrophenol \( t_1 \).

4. **Consider the Mixture at Temperature \( t \)**:
- When the mixture is heated at temperature \( t \) (where \( t_1 < t < t_2 \)), the vapor will contain more of the component with the lower boiling point, which is ortho-nitrophenol.
- This is because at temperatures below the boiling point of para-nitrophenol, ortho-nitrophenol will evaporate more readily due to its lower boiling point.

5. **Conclusion**:
- Therefore, the vapor will significantly contain more ortho-nitrophenol than para-nitrophenol.

### Final Answer:
The vapor will significantly contain more **ortho-nitrophenol** than para-nitrophenol.