A certain compound when burned gives three oxides. The first turned lime water milky, the second turned anhydrous `CuSO_4` blue and the third formed an aqueous solution of low pH. The elements present in the compound are

Options

A. (a) C,S,Ca
B. (b) N,S,K
C. (c) C,H,S
D. (d) C,H,Ca

Answer

To solve the question, we need to analyze the information given about the compound and the oxides it produces when burned.

### Step-by-Step Solution:

1. **Identify the First Oxide:**
- The first oxide turns lime water milky.
- Lime water is a solution of calcium hydroxide (Ca(OH)₂), and when carbon dioxide (CO₂) is bubbled through it, it reacts to form calcium carbonate (CaCO₃), which is a white precipitate.
- Therefore, the first oxide is **CO₂**.

2. **Identify the Second Oxide:**
- The second oxide turns anhydrous copper sulfate (CuSO₄) blue.
- Anhydrous copper sulfate is white, but when it reacts with water, it forms hydrated copper sulfate (CuSO₄·5H₂O), which is blue.
- This indicates that the second oxide must be **H₂O** (water).

3. **Identify the Third Oxide:**
- The third oxide forms an aqueous solution of low pH.
- A low pH indicates an acidic solution. Sulfur dioxide (SO₂) is known to form an acidic solution when dissolved in water, resulting in sulfurous acid (H₂SO₃).
- Thus, the third oxide is **SO₂**.

4. **Determine the Elements in the Compound:**
- From the identified oxides (CO₂, H₂O, and SO₂), we can deduce the elements present in the original compound.
- CO₂ contains carbon (C) and oxygen (O).
- H₂O contains hydrogen (H) and oxygen (O).
- SO₂ contains sulfur (S) and oxygen (O).
- Therefore, the compound must contain **carbon (C)**, **hydrogen (H)**, and **sulfur (S)**.

5. **Choose the Correct Option:**
- Now, we need to match the identified elements with the given options:
- Option A: C, S, Ca (Incorrect, as it contains Calcium)
- Option B: N, S, K (Incorrect)
- Option C: C, H, S (Correct)
- Option D: C, H, Ca (Incorrect, as it contains Calcium)
- The correct answer is **Option C: C, H, S**.

### Final Answer:
The elements present in the compound are **Carbon (C), Hydrogen (H), and Sulfur (S)**.

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