In reaction `C_(2)H_(5)OH+Hxoverset(ZnX_(2))rarrC_(2)H_(5)X+H_(2)O` the order of reactivity of HX is :

Options

A. `HCl gt HBr gt HI`
B. `HI gt HBr gt HCl`
C. `HBr gt HCl gt HI`
D. `HI gt HCl gt HBr`

Answer

To determine the order of reactivity of HX in the reaction \( C_2H_5OH + HX \overset{ZnX_2}{\rightarrow} C_2H_5X + H_2O \), we need to analyze the nucleophilicity of the halide ions involved (I^-, Br^-, Cl^-).

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactants are ethanol (\( C_2H_5OH \)) and a hydrogen halide (\( HX \)).
- The products are an alkyl halide (\( C_2H_5X \)) and water (\( H_2O \)).

2. **Understand the Role of HX**:
- In this reaction, \( HX \) provides the halide ion \( X^- \) which acts as a nucleophile.
- The strength of the nucleophile will influence the reactivity of the reaction.

3. **Consider Nucleophilicity**:
- Nucleophilicity is the ability of a species to donate a pair of electrons to an electrophile.
- It is inversely related to the electronegativity of the atom carrying the negative charge.

4. **Order of Electronegativity**:
- The electronegativity of halogens decreases in the order: \( F > Cl > Br > I \).
- Therefore, the order of nucleophilicity for the halide ions (in terms of their ability to act as nucleophiles) is:
- I^- > Br^- > Cl^-.

5. **Determine the Order of Reactivity**:
- Since I^- is the most nucleophilic and Cl^- is the least, the order of reactivity of the hydrogen halides (HX) based on their nucleophilicity is:
- HI > HBr > HCl.

6. **Select the Correct Option**:
- From the options provided:
1. HCl > HBr > HI
2. HI > HBr > HCl (this is correct)
3. HBr > HCl > HI
4. HI > HCl > HBr
- The correct order of reactivity is given in option 2: HI > HBr > HCl.

### Final Answer:
The order of reactivity of HX is: **HI > HBr > HCl** (Option 2).