Which compound among the following has lowest oxidation number of chlorine ?

Options

A. `ClF_(3)`
B. `HClO_(3)`
C. HCl
D. HOCl

Explanation

To determine which compound has the lowest oxidation number of chlorine among the given options, we will calculate the oxidation number of chlorine in each compound step by step.

### Step 1: Analyze ClF3
- Let the oxidation number of chlorine be \( X \).
- The oxidation number of fluorine (F) is always \(-1\).
- The compound has 3 fluorine atoms, so the equation is:
\[ X + 3(-1) = 0 \]
- Simplifying this gives:
\[ X - 3 = 0 \implies X = +3 \]

### Step 2: Analyze HClO3
- Let the oxidation number of chlorine be \( X \).
- The oxidation number of hydrogen (H) is \( +1 \) and for oxygen (O) it is \(-2\).
- There are 3 oxygen atoms, so the equation is:
\[ +1 + X + 3(-2) = 0 \]
- Simplifying this gives:
\[ +1 + X - 6 = 0 \implies X - 5 = 0 \implies X = +5 \]

### Step 3: Analyze HCl
- Let the oxidation number of chlorine be \( X \).
- The oxidation number of hydrogen (H) is \( +1 \).
- The equation is:
\[ +1 + X = 0 \]
- Simplifying this gives:
\[ X + 1 = 0 \implies X = -1 \]

### Step 4: Analyze HOCl
- Let the oxidation number of chlorine be \( X \).
- The oxidation number of oxygen (O) is \(-2\) and hydrogen (H) is \( +1 \).
- The equation is:
\[ +1 + X + (-2) = 0 \]
- Simplifying this gives:
\[ +1 + X - 2 = 0 \implies X - 1 = 0 \implies X = +1 \]

### Summary of Oxidation Numbers
- ClF3: \( +3 \)
- HClO3: \( +5 \)
- HCl: \( -1 \)
- HOCl: \( +1 \)

### Conclusion
Among these compounds, the one with the lowest oxidation number of chlorine is **HCl**, which has an oxidation number of \(-1\).