An element X burns with a brilliant blue flame in the presence of oxygen to form Y.Y turns acidified potassium dichromate paper green. Identify X and Y.

Options

A. Nitrogen, nitrogen dioxide
B. Sulphur, sulphur dioxide
C. Phosphorus, phosphorus pentoxide
D. Sodium, sodium oxide

Explanation

To solve the question, we need to identify the element X that burns with a brilliant blue flame in the presence of oxygen and the compound Y that turns acidified potassium dichromate paper green.

### Step-by-Step Solution:

1. **Identify Element X:**
- The question states that element X burns with a brilliant blue flame in the presence of oxygen.
- One known element that burns with a blue flame is **Sulfur**. When sulfur burns in oxygen, it produces sulfur dioxide (SO₂), which is known to produce a blue flame.

2. **Identify Compound Y:**
- When sulfur burns in oxygen, it forms sulfur dioxide (SO₂).
- The question also mentions that Y turns acidified potassium dichromate paper green.
- Sulfur dioxide (SO₂) is an acidic oxide and can reduce potassium dichromate (K₂Cr₂O₇) in acidic conditions, leading to the formation of chromium(III) ions, which give a green color.

3. **Final Identification:**
- Therefore, we can conclude that:
- Element X is **Sulfur (S)**.
- Compound Y is **Sulfur Dioxide (SO₂)**.

### Summary:
- **X = Sulfur (S)**
- **Y = Sulfur Dioxide (SO₂)**