Which of the following oxide is least acidic

Options

A. `P_(4)O_(6)`
B. `P_(4)O_(10)`
C. `As_(4)O_(6)`
D. `As_(4)O_(19)`

Answer

To determine which of the given oxides is least acidic, we need to analyze the acidic character of the oxides of phosphorus and arsenic. Here’s a step-by-step solution:

### Step 1: Identify the Oxides
First, we need to identify the oxides of phosphorus and arsenic that are being compared. The common oxides of phosphorus are:
- Phosphorus trioxide (P₄O₆)
- Phosphorus pentoxide (P₄O₁₀)

The common oxides of arsenic are:
- Arsenic trioxide (As₂O₃)
- Arsenic pentoxide (As₂O₅)

### Step 2: Understand Acidic Character
The acidic character of oxides generally increases with the oxidation state of the element. Higher oxidation states lead to stronger acidic behavior.

### Step 3: Determine the Oxidation States
- For phosphorus:
- In P₄O₆, phosphorus has an oxidation state of +3.
- In P₄O₁₀, phosphorus has an oxidation state of +5.

- For arsenic:
- In As₂O₃, arsenic has an oxidation state of +3.
- In As₂O₅, arsenic has an oxidation state of +5.

### Step 4: Compare Acidic Strength
From the oxidation states:
- P₄O₁₀ (+5) is more acidic than P₄O₆ (+3).
- As₂O₅ (+5) is more acidic than As₂O₃ (+3).

### Step 5: Analyze the Trend
As we move down the group in the periodic table (from phosphorus to arsenic), the acidic character of oxides decreases. This is due to the increasing size of the atoms and the decreasing electronegativity, which weakens the ability to donate protons (H⁺ ions).

### Step 6: Conclusion
Among the oxides listed:
- P₄O₁₀ (most acidic)
- P₄O₆ (less acidic)
- As₂O₅ (more acidic)
- As₂O₃ (least acidic)

Thus, the oxide that is least acidic is **As₂O₃**.

### Final Answer
The least acidic oxide is **As₂O₃**.

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