The weakest acid is

Options

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

Answer

To determine the weakest acid among the given halogen acids (HF, HCl, HBr, HI), we need to analyze their ability to release H⁺ ions. Here’s a step-by-step solution:

### Step 1: Understand what an acid is
An acid is defined as a substance that can donate H⁺ ions (protons) in solution. The strength of an acid is determined by how readily it donates these protons.

**Hint:** Remember that the easier it is for an acid to release H⁺ ions, the stronger the acid is.

### Step 2: Identify the halogen acids
The halogen acids we are considering are:
- HF (hydrofluoric acid)
- HCl (hydrochloric acid)
- HBr (hydrobromic acid)
- HI (hydroiodic acid)

**Hint:** List the acids clearly to avoid confusion when analyzing their properties.

### Step 3: Analyze the bond strength
The strength of the H-X bond (where X is a halogen) plays a crucial role in determining acid strength. The bond strength decreases as we move down the group in the periodic table:
- HF has the strongest bond due to the small size and high electronegativity of fluorine.
- HCl has a weaker bond than HF.
- HBr has an even weaker bond than HCl.
- HI has the weakest bond among them.

**Hint:** Consider how bond strength affects the ability to release H⁺ ions; weaker bonds make it easier to release protons.

### Step 4: Determine the acid strength
Since HF has the strongest bond, it is the least likely to release H⁺ ions, making it the weakest acid. Conversely, HI has the weakest bond, allowing it to release H⁺ ions more easily, thus making it the strongest acid among the halogen acids.

**Hint:** Compare the bond energies; the weaker the bond, the stronger the acid.

### Step 5: Conclusion
Based on the analysis, the weakest acid among the given halogen acids is HF (hydrofluoric acid).

**Final Answer:** HF (hydrofluoric acid) is the weakest acid.