Which of the following ions will liberated iodine when trated with KI?

Options

A. `Cu^(2+)`
B. `Fe^(2+)`
C. `Pb^(2+)`
D. `Sn^(2+)`

Answer

To solve the question of which ions will liberate iodine when treated with potassium iodide (KI), we can follow these steps:

### Step 1: Understand the Role of Iodide Ion (I⁻)
The iodide ion (I⁻) is a strong reducing agent. This means it can donate electrons to other species, which may lead to the liberation of iodine (I₂) under certain conditions.

**Hint:** Remember that reducing agents tend to lose electrons and can cause other substances to be reduced.

### Step 2: Identify the Oxidizing Agents
To liberate iodine from iodide ions, we need to identify which ions can act as oxidizing agents. An oxidizing agent is a substance that gains electrons in a chemical reaction.

**Hint:** Look for ions that are known to be strong oxidizers, as they will facilitate the oxidation of iodide ions.

### Step 3: Analyze the Given Ions
We need to analyze the ions provided in the options. Common ions that can act as oxidizing agents include Cu²⁺ (copper(II) ions), Cl₂ (chlorine gas), and others.

**Hint:** Recall that transition metal ions, particularly in higher oxidation states, often act as strong oxidizing agents.

### Step 4: Reaction of Iodide with Oxidizing Agents
The reaction of I⁻ with a strong oxidizing agent like Cu²⁺ can be represented as follows:
\[ 2 I^- + Cu^{2+} \rightarrow Cu^+ + I_2 + 2 e^- \]
In this reaction, the iodide ions are oxidized to iodine (I₂), and Cu²⁺ is reduced to Cu⁺.

**Hint:** Write down the half-reactions to visualize the electron transfer process.

### Step 5: Conclusion
From the analysis, we conclude that only ions that can act as strong oxidizing agents will liberate iodine when treated with KI. In this case, Cu²⁺ is the only ion that fits this criterion.

**Final Answer:** The ion that will liberate iodine when treated with KI is Cu²⁺.

### Summary of Steps:
1. Understand the reducing nature of I⁻.
2. Identify potential oxidizing agents.
3. Analyze the reactions between I⁻ and the oxidizing agents.
4. Conclude which ions can liberate iodine.