Out of all the halogen hydracids, the weakest hydracid is:

Options

A. HI
B. HBr
C. HF
D. HCl

Explanation

To determine the weakest halogen hydracid among HF, HCl, HBr, and HI, we need to analyze their ability to donate H⁺ ions. Here's a step-by-step solution:

### Step 1: Understand the Definition of Acids
An acid is defined as a substance that can donate H⁺ ions. The strength of an acid is determined by how easily it can donate these ions.

**Hint:** Remember that strong acids dissociate completely in solution, while weak acids do not.

### Step 2: Identify the Halogen Hydracids
The halogen hydracids in question are:
- HF (Hydrofluoric acid)
- HCl (Hydrochloric acid)
- HBr (Hydrobromic acid)
- HI (Hydriodic acid)

**Hint:** List the acids clearly to avoid confusion later.

### Step 3: Analyze Bond Strength
The bond strength between hydrogen and the halogen in each acid affects how easily the acid can donate H⁺ ions. As we move down the group in the periodic table, the size of the halogen increases, leading to weaker H-X bonds:
- HF: Strong bond (small size of F)
- HCl: Weaker bond than HF
- HBr: Weaker bond than HCl
- HI: Weakest bond (largest size of I)

**Hint:** Consider how atomic size affects bond strength; larger atoms lead to weaker bonds.

### Step 4: Determine Bond Dissociation Enthalpy
The bond dissociation enthalpy is the energy required to break the bond and release H⁺ ions. Weaker bonds require less energy to break:
- HI has the weakest bond and thus the lowest bond dissociation enthalpy, making it the strongest acid.
- HF has the strongest bond and thus the highest bond dissociation enthalpy, making it the weakest acid.

**Hint:** Recall that lower bond dissociation enthalpy means the acid is stronger because it can release H⁺ ions more easily.

### Step 5: Conclusion
Based on the analysis of bond strength and dissociation enthalpy, HF is the weakest halogen hydracid because it does not release H⁺ ions easily compared to the others.

**Final Answer:** The weakest halogen hydracid is **HF**.