Arrange the following in the order of property indicated for each set :
(i) `F_(2), Cl_(2) Br_(2),I_(2)`- increasing bond dissociation enthalpy.
HF,HCl, HBr, HI- increasing acid strength.
`NH_(3), PH_(3), AsH_(3), SbH_(3), BiH_(3)`- increasing base strength.

Answer

To solve the problem, we need to arrange the given sets of compounds according to the specified properties. Let's break it down step by step.

### (i) Increasing Bond Dissociation Enthalpy: `F2, Cl2, Br2, I2`

1. **Understanding Bond Dissociation Enthalpy**: This is the energy required to break a bond in a molecule. Generally, smaller atoms with stronger bonds will have higher bond dissociation enthalpy.

2. **Analyzing the Halogens**:
- **F2 (Fluorine)**: Although fluorine is small, it has high electron-electron repulsion due to its small size, leading to a weaker bond.
- **Cl2 (Chlorine)**: Chlorine has a stronger bond compared to fluorine due to lower repulsion.
- **Br2 (Bromine)**: Bromine has a weaker bond than chlorine but stronger than iodine.
- **I2 (Iodine)**: Iodine is the largest atom, leading to the weakest bond.

3. **Arranging in Order**: Based on the above analysis, the order of increasing bond dissociation enthalpy is:
- **I2 < Br2 < F2 < Cl2**

### (ii) Increasing Acid Strength: HF, HCl, HBr, HI

1. **Understanding Acid Strength**: Acid strength is related to how easily the hydrogen ion (H+) can be released. Larger halogens form weaker bonds with hydrogen, making it easier to release H+.

2. **Analyzing the Acids**:
- **HF (Hydrofluoric Acid)**: Strong bond due to small size of F, making it a weak acid.
- **HCl (Hydrochloric Acid)**: Weaker bond than HF, stronger acid than HF.
- **HBr (Hydrobromic Acid)**: Even weaker bond, stronger acid than HCl.
- **HI (Hydroiodic Acid)**: Weakest bond, making it the strongest acid.

3. **Arranging in Order**: The order of increasing acid strength is:
- **HF < HCl < HBr < HI**

### (iii) Increasing Base Strength: NH3, PH3, AsH3, SbH3, BiH3

1. **Understanding Base Strength**: Base strength is related to the ability to accept protons (H+). Smaller atoms with lone pairs are better bases.

2. **Analyzing the Hydrides**:
- **NH3 (Ammonia)**: Small size and high electronegativity make it a strong base.
- **PH3 (Phosphine)**: Larger than NH3, weaker base.
- **AsH3 (Arsine)**: Even larger, weaker base than PH3.
- **SbH3 (Stibine)**: Larger than AsH3, weaker base.
- **BiH3 (Bismuthine)**: Largest and least capable of accepting protons, making it the weakest base.

3. **Arranging in Order**: The order of increasing base strength is:
- **BiH3 < SbH3 < AsH3 < PH3 < NH3**

### Final Arranged Orders

1. **Increasing Bond Dissociation Enthalpy**: I2 < Br2 < F2 < Cl2
2. **Increasing Acid Strength**: HF < HCl < HBr < HI
3. **Increasing Base Strength**: BiH3 < SbH3 < AsH3 < PH3 < NH3