In the reaction `C_(2)H_(5)OH + " HX " overset(ZnX_(2))(rarr) C_(2)H_(5)X,` the order of the reactivity of HX is :

Options

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

Answer

To determine the order of reactivity of HX in the reaction \( C_2H_5OH + HX \overset{ZnX_2}{\rightarrow} C_2H_5X \), we need to analyze the reactivity of different hydrogen halides (HX) with ethanol (C2H5OH).

### Step-by-Step Solution:

1. **Identify the Reaction Type**:
The reaction is a nucleophilic substitution where the hydroxyl group (OH) of ethanol is replaced by a halogen (X) from HX. The presence of ZnX2 facilitates this substitution.

**Hint**: Understand that nucleophilic substitution involves replacing one group with another, in this case, OH is replaced by a halogen.

2. **Consider the Halogens**:
The halogens involved can be fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). The hydrogen halides we are considering are HCl, HBr, and HI.

**Hint**: Recall the halogens' positions in the periodic table and their properties, particularly their bond strengths.

3. **Evaluate Bond Strength**:
The bond strength of HX decreases as we move down the group in the periodic table:
- H-F bond is the strongest.
- H-Cl bond is weaker than H-F.
- H-Br bond is weaker than H-Cl.
- H-I bond is the weakest.

**Hint**: The weaker the bond, the easier it is to dissociate and release the halide ion (X⁻).

4. **Analyze Reactivity**:
- **HI**: The bond between H and I is the weakest, making it the most reactive. The iodine ion (I⁻) can easily participate in the nucleophilic substitution.
- **HBr**: The bond is stronger than HI but weaker than HCl, making it less reactive than HI but more reactive than HCl.
- **HCl**: The bond is the strongest among the three, making it the least reactive in this context.

**Hint**: Remember that the ease of reaction is related to how easily the halide ion can be generated from the hydrogen halide.

5. **Determine the Order of Reactivity**:
Based on the bond strengths and the ability to generate halide ions, the order of reactivity of HX is:
\[ HI > HBr > HCl \]

**Hint**: Think about how the size of the halogen affects the bond strength and the ability to act as a nucleophile.

### Final Answer:
The order of reactivity of HX in the given reaction is:
\[ \text{HI} > \text{HBr} > \text{HCl} \]