Which of the following statements is not true

Options

A. HF is a stronger acid than HCl
B. Among halide ions, iodide is the most powerful reducing agent
C. Fluorine is the only halogen that does not show a variable oxidation state
D. HOCl is a stronger acid than HOBr

Explanation

To determine which of the statements is not true, we will analyze each statement one by one based on our knowledge of the properties of acids and halogens.

### Step 1: Analyze the first statement
**Statement:** "It is a stronger acid than HCl."

- **Analysis:** HCl (hydrochloric acid) is a strong acid. Generally, acids are compared based on their ability to donate protons (H⁺ ions). If the statement claims that another acid is stronger than HCl without specifying which acid it refers to, it is likely false unless it is a well-known stronger acid like H₂SO₄ (sulfuric acid). Therefore, this statement is likely false.

### Step 2: Analyze the second statement
**Statement:** "Iodine is the most powerful reducing agent."

- **Analysis:** In the context of halogens, iodine is indeed considered a reducing agent, but it is not the strongest. Fluorine is the strongest oxidizing agent and does not act as a reducing agent. Thus, this statement is misleading and can be considered false.

### Step 3: Analyze the third statement
**Statement:** "Fluorine is the only halogen that does not show variable oxidation states."

- **Analysis:** This statement is true. Fluorine typically exhibits a -1 oxidation state and does not show positive oxidation states due to its high electronegativity. Other halogens like chlorine, bromine, and iodine can exhibit multiple oxidation states.

### Step 4: Analyze the fourth statement
**Statement:** "H-O-Z is a stronger acid than H-O-B."

- **Analysis:** This statement compares the acids HClO (hypochlorous acid) and HBrO (hypobromous acid). Generally, the strength of oxoacids increases with the electronegativity of the central atom. Since chlorine is more electronegative than bromine, HClO is indeed a stronger acid than HBrO. Thus, this statement is true.

### Conclusion
After analyzing all the statements, we find that the first statement ("It is a stronger acid than HCl") and the second statement ("Iodine is the most powerful reducing agent") are not true. However, since the question asks for one statement that is not true, we can conclude:

**The statement that is not true is:** "It is a stronger acid than HCl."